Only Monera kingdom has P cells ,rest Protista +fungi +plants+ animals have E cells
Monera includes bacteria and all its forms(cyanobacteria + archaebacteria + methanogens + pathogenic forms + mycoplasma
Pathogenic forms → T.B, Antharax, Typhoid
Mycoplasma and Pleuro pneumonia like organism are smallest living cells/beings
Protista
Unicellure Eukaryotes
Eg of Eukaryotes → Euglena, Diatoms, Dinoflagellates, Protozoans, Slime Moulds
Diatoms, Dinoflagellates → Found in Phytoplanktons (ocean) are chief producers
Amoeba, Paramenium, Plasmodium → All are protozoa
Slime moulds are decomposers
Fungi
Can be unicellular and multicellular but maximum forms (more than 99% are multicellular)
Moulds → are colony of fungu
Yeast
not an individual living being
it’s a terms used for unicecullar form of fungus
Example : Bakers Yeast, Saccharomyces → used in bakery industry && fermentation of Alcoho
Example of Fungus → Mushroom, Penicillium
Aflatoxins are moulds of Aspergillus ,aflatoxins released some toxins which damage stored food grains
💡
Protista ,fungi,plants ,animals all are EK
✅Unit 1.7 : The Biological Basis of Life
From Handwritten Class Notes
✅Unit 1.4 : Human Evolution & Emergence of Man
Introduction to Evolution
From Class Handwritten Notes
Evidences for Evolution
Theories of Organic Evolution
Pre Darwinian (3)
Spontaneous Theroeis (Not in Syllabus)Special Creation (Not in Syllabus)Lamarckism (In Syllabus)
Alternate Names
Theory of Inheritance of Acquired Characters - This emphasises the concept of traits acquired or lost due to environmental interaction being passed down generations.
Use and Disuse of Organs - This concept highlights the idea that the functionality of organs influences their development and inheritance.
Proponent and Primary Source
The theory was proposed by Jean-Baptiste Lamarck in his seminal work, ‘Philosophie Zoologique’.
Identifying Lamarck and his work underscores the origin of the theory, crucial for understanding its historical context and initial formulation.
Core Propositions of Lamarck’s Theory
Internal Vital Force:
Organisms possess an inherent force that:
Promotes growth,
Enhances characteristics, and
Drives the development of adaptive features.
This force is integral to the process of evolution.
Effect of Environment & New Needs:
Environmental and climatic changes induce modifications in organisms’ traits due to:
The emergence of new requirements caused by environmental shifts, and
Subsequent structural and behavioral adaptations.
Use and Disuse of Organs:
Organ functionality determines its evolutionary fate:
Regular usage leads to development and retention,
Disuse results in degeneration.
Inheritance of Acquired Characters:
Traits acquired within a lifetime, due to the factors mentioned above, are:
Passed down to successive generations, and
Accumulate over time to form new species.
Lamarck’s Exemplifications:
Elongation of Neck in Giraffes:
Environmental changes (food scarcity) led ancestors of modern giraffes to adapt (longer necks) for survival.
Increased Speed in Deer:
Predation pressure necessitated speed enhancement in ancestral deer for survival.
Critiques
Lamarck's propositions, especially regarding the internal vital force and the inheritance of acquired traits, were criticized due to:
Lack of empirical evidence, and
Contradictions with later genetic findings, particularly Mendel’s laws of inheritance.
Concluding Significance
Despite criticisms, Lamarck’s theory remains a significant precursor in evolutionary thought, paving the way for subsequent scientific discourse and discoveries in organic evolution.
Darwinian
Darwin's Theory of Natural Selection
Darwin's Theory of Natural Selection: This pivotal concept in evolutionary biology is also known by various names:
Darwinism - Commonly used term to describe the theory.
Theory of Natural Selection by Charles Darwin - Emphasizes the originator of the concept.
Background:
Voyage on the HMS Beagle: Charles Darwin's revolutionary ideas stemmed from observations during this journey.
Galapagos Islands: Key location where Darwin studied finches and other wildlife, which significantly influenced his theories.
Key Postulates of Darwin's Theory:
The theory is built on five fundamental pillars:
Rapid Multiplication: Species have a high reproductive potential, which leads to a struggle for survival due to overpopulation.
Stability of Species/Population: Despite rapid multiplication, populations remain roughly stable in size.
Limited Resources: Environmental resources are limited, leading to a "struggle for existence" among individuals.
This struggle results in natural selection and the emergence of new species.
Variations: Individuals within a species exhibit variations, some of which may be beneficial for survival and reproduction.
Inheritance of Useful Variation: Beneficial traits are heritable and are thus passed on to the next generation, driving evolutionary change.
Criticism of Darwin's Theory:
Despite its significance, the theory has faced various criticisms, notably:
Lack of Knowledge on Heredity: Darwin's theory did not incorporate the principles of genetic inheritance, as they were unknown at his time.
No Argument for the Arrival of the Fittest: The theory explains the survival of the fittest but not the arrival of the fittest.
Discontinuous Variation and Mutation: Subsequent research highlighted the role of mutation and discontinuous variation in the formation of new species and evolution, aspects not explained by Darwin.
Conclusion:
Despite recognizing the inadequacies of his theory, Darwin remained convinced that natural selection was the primary, though not sole, mechanism behind evolutionary changes such as modifications, variations, speciation, and evolution
Post Darwinian
Mutation Theory by Hugho De Vries
Introduction
Mutations are sudden ,random, directionless changes in the genetic makeup leading to changed characters
De vires termed mutations as saltations. He gave his theory of evolution based on his studies on evening primrose (plants)
He considered this saltation/mutations as discontinuous variations
De Vries started by criticising Darwin saynig that discontinued variations of Darwin are small scale variations
these are not strong enough for species to evolve and these small scale variations scale cannot be transferred to next generation
He termed saltations as large scale varaitions which are strong enough that it can lead to changes in species. these large scale can be transferred to the next generation
Proposition by De Vries
Mutations are the raw material for evolution and are actually the discontinuous variations
They appear all of a sudden and became operational immediately
There is No fixed direction/time period for mutations
Unlike Darwin’s continuous variations mutations are not always present they appear all of a sudden
Same type of mutation can occur in multiple individuals of a species
multiple mutations can occur within the same individual
All the mutations are inheritable but only the useful once are selected by nature and the lethal ones (which will kill the existence of the species) are eliminated
Evolution is a jerky and discontinuous process
Criticism to Mutation Theory
Mutations can lead to evolutionary changes but are not the only force behind these changes
also evolutionary changes can move on with a faster speed/with the slower one. Evolution is an ongoing process
Mutations theory gave direct attention to concept of evolution as a central theme which promoted multiple studies for evolutionary changes and latter evolutionist agreed upon this thing that evolution cannot be result of one or two factors but is involving multiple others
Modern/Synthetic Theory of Evolution(Neo Darwinism)
Introduction
It is the most accpted theory of evolution
Not considering evolution as a result of one or two factors but as an outcome of multiple factors acting together like
natural selection
mutations
hereditary changes
recombinations
a collective impact of these factors can lead to speciation and evolution
This theory was supported by Stebbins, Ernst Myers, Dobzhanskey, Sewall Wright
Synthetic theory of evolution is a synthesis of evolutionary concepts by picking up expectable postulates from various theories of evolution as well as incorporation of addition aspects
5 Important Postulates
1. Genetic Variation in Population
Mutations
Sudden Inheritable random directionless changes, leading to change in genetic makeup
Mutations can be chromosomal mutations and gene mutations
Genetic recombination (4)
Gene recombinations can take place due to multiple reasons leading to accumulations of various and addition to new allies to populations
Various Factors are
Dual Parenthood / Parentage
Dual parentage is one of the significant reason for gene recombination when genetic information from 2 different parents is leading to accumulations of variations
Crossing Over
Crossing over during miosis of
cell division
Random Fusion of Gamets
Random fusion of gametes leading to mixing of genetic character, leading to mixup of genetic information
Independent Assortment
Independent assortment of genes and chromosomes
Gene migration / Gene Flow
genes with migation of humans moved from location to another, then mating with native group
this can take place due to multiple reasons and additon of new alleles
this led to movement of individuals of a species from one place to another and exchange of genetic information with the new population will lead to addition of new allies in the in the local gene pool
Genetic Drift / Sewall Wrightly Effect
Sewall wright was an American geneticist
Genetic drift is defined as drastic change in gene or alleles frequency when population size became very small due to disease disaster war etc
altering the gene frequency of remaining population causing large scale variations
Genetic drift occurs in all populations at a natural pace but it is most well marked in small isolated populations which can be understood with two principles
Founder Effect/Founder Principle → by Sewall Right
When a small grp of populations from a species called as founders leave their native location.
They then Settle at a different geography and climate
They will acquire new characters to fulfil the demands of local climate and with the period of time the ‘founders’ will have different gene or allele frequency from the parent population
some times this isolation can lead to speciation/formation of new species
Genetic Bottle Neck/Bottle Neck Effect → By Stebbins
Stebbeins considered genetic bottleneck as a cyclic phenomena of
decrease or increase in the population size
When population is at decline there will be decline in the gene or alleles frequency and this can lead to extinction of the species but a natural balance created by fixation of certain genes within the population will bottleneck the extinction and the former richness will be restabilised with changed or new allele frequencies
this process will be repeated again and again and this genetic bottleneck would act as an evolutionary force
2. Isolation
It is the Prevention of random mating amongst the interbreeding groups due to various factors like
Geographical Barriers
Climatic Barriers
Physiological / Behavourial
Occurence of Incompatibility at various levels
Two prominent aspects of isolation
Geographical Isolation
Geographical / Climatic / Environmental isolation takes place when individuals of the
same species
matching species
sister species
are not able to cross bred due to geographical barriers like islands,mountains,dense forest etc
These geographically isolated populations will develope locally adapted genetic pool in their population forming Demes
Demes is : a local population of closely related interbreeding organisms
With subsequent generations these local populations will develop different characters due to accumulation of variations contributing to speciation and evolution
Reproductive Isolation
It is the prevention of interbreeding between populations of different species to maintain characters of a particular species and preventing the abrupt changes in the gene frequencie
Reproductive Isolation can occur through
behavioural factors
physiological factors
mechanical factors
genetic factors
Seasonal isolation
females having different heat period during different seasons in different species not allowing males of other species to have a random matin
Incompatibility between members of differenr species is another significant factor acting as a reproductive isolation barrie
In some instances
mating takes place between members of different populations but fertilization does not occur
even if fertilization occurs no hybrid offspring is formed
In some cases even the hybrids are formed but they cannot further reproduce to have next generations i.e the hybrid is sterile
Explantion
physiological/behavioural/mechanical/genetic species are present
in the same geography but due to difference in body mechanism
they can have different heating period
There can be differences in
male 1 and male 2 .female cannot have different behavioural type of
males
Example
Male Donkey and Female Horse(Mare) mate to form a hybrid called Mule this which is sterile
Male Horse and Female donkey mate to form a hybrid called Henny which is sterile
These steriles will not form further generation
3. Heredity & Variation
Heredity & Variation is transfer of characters from parents to offspring’s and the differences being accumulated is generations per generations which can act as significant factor in evolution
Genetics Deals with 2 things – Heredity and Variations
Heredity is transfer of characters from parents to off springs
Variations are the differences accumulated in offspring
In general, useful hereditary information is retained and is kept generations per generations and the less useful characters are discarded. These changes are also leading to speciation and evolution.
4. Natural Selection
Introduction
Natural Selection was given by Charles Darwin
One of the most widely accepted concept for evolution
It was guided by survival of the fittest
As a result of continuous variations
Natural Selection to Selection
This Natural Selection was replaced with the term Selection as the
process by which better adapted individuals/populations will survive
and reproduce more and the less adapted species or population will
not have much reproductive capability
Selection depends on the existence of Phenotypic variations in a
population
Three Types of Selection Process in Population
Stabilising / Balancing Selection
Min / No Contribution
It favours avg/stable forms of individuals like the avg size reducing the variation
Reduction in variation=Stability= No changes=no contribution /minimum contribution in evolution
Population changes are tilted to one particular direction like favouring either the large sized/small sized individuals
this unidirectional progressive tilt will contribute to evolution but in a mild manner
Disruptive / Diversifying Selection
Maximum Contribution
This type of selection favours both the extremes like the small and large size individuals
and the stable avg size populations are gradually wiped out so evolution can go in any direction avoiding the stability and favouring the change
It is opposite to that of stabilizing selection
5. Speciation
Speciation is Formation of New Species
Populations of a species present in different environmental conditions
or are having isolations due to physiological or behavioural barriers can lead to formation of new species as a result of accumulation of variations
Speciation are of Two Types
Geographical Isolation
Speciation due to Geographical Barrier is called as Allpatic Speciation
Reproductive Isolation
Speciation due to Reproductive Isolation is called as Sympatic Variation
Differences between Darwinism & Lamarckism
Aspect
Darwinism
Lamarckism
Theory Basis
Based on natural selection
Based on acquired characteristics
Vital Force
Internal vital force was mentioned
Species will accommodate
Source of Variation
Random mutations
New needs and desires
Character Acquisition
New needs and desires will give rise to new characters
Continuous variations will give rise to new character
Use and Disuse of Organs
Did not support the use and disuse of organs
Believed in use and disuse of organs
Inheritance
Inheritance of all acquired characters
Only the useful variations are being transmitted
Natural Selection
Emphasised on survival of the fittest
Nothing mentioned about this
Time Frame
Believed evolution to be slow and gradual
Believed evolution could occur relatively quickly due to acquired characteristics
Adaptation
Organisms adapt over generations due to environmental pressures and natural selection
Organisms adapt within their lifetime and pass these adaptations to their offspring
Comparison Micro and Macro Evolution
Criteria
Micro Evolution
Macro Evolution
Scale of Change
Small changes in the course of evolution
Large-scale changes in evolution
Time Period
Shorter period of time
Longer period suggested
Population Scope
Takes place in a small population
In a large population or entire species or multiple species
Encompasses highest level changes taking place involving the growth of one or more species.
Examples
1. Bacteria getting resistant to antibiotics
2. Development of new variant of COVID-19
3. Mosquitoes becoming malaria-resistant over short periods of time
1. Human evolution from earliest known stages of Dryopithecus and Ramapithecus to modern men
2. Origin of flowering (angiosperm) plants
Causes and Visibility of Change
Can take place due to genetic drift, genetic recombination, mutations, etc.
Not easy to witness as change is very gradual or slow; may involve even atmospheric changes
Important Evolutionary Concepts (7)
Key Concepts
Dollo’s Law : Evolution is irreversible; it operates unidirectionally.
Cope’s Rule : Cope's Rule posits an evolutionary trend toward an increase in body size in animal lineages over geological time, suggesting that larger size may offer organisms a competitive advantage in survival and reproduction.
Gause’s Rule : Two species competing for the same limiting resource cannot coexist at constant population values. When one species has even the slightest advantage or edge, the other will eventually be driven to extinction.
Bergmann’s Rule: Bergmann's Rule is an ecogeographical principle stating that within a broad taxonomic group, species or populations of larger size are found in colder environments, while those of smaller size are found in warmer regions.
Mosaic Evolution: The key concept is that evolutionary development is not uniform across an organism's body or across species; instead, different parts or features can evolve independently and at different rates. This means that various traits of an organism, such as the skeletal structure, brain size, or internal organs, do not evolve in a synchronous or linear fashion. Instead, each trait can follow its own evolutionary trajectory, leading to a "mosaic" of features that may be at different stages of evolutionary development at any given time.
Adaptive Radiation: Rapid diversification of a single ancestral lineage into multiple new forms or species, often driven by environmental changes and resulting in varied traits suited to specific niches.
Adaptive Convergence: Independent evolution of similar traits in species of different lineages, often due to facing similar environmental challenges or ecological niches.
Parallelism: Simultaneous evolution of similar traits in closely related species, stemming from a common ancestor but occurring in different contexts or regions.
Dollo's Law by Louis Dollo
Introduction
Originator: Louis Dollo, a Belgium Paleontologist.
Key Concept: Evolution is irreversible; it operates unidirectionally.
Principle Details
Irreversibility of Evolution:
Organisms or species do not revert to a former state, even if previous conditions recur.
Genetic Mutation:
After a change in allele or gene frequency (n alleles mutated), a reversal is impossible.
Simplicity of Concept:
Essentially, reverse evolution does not occur.
Richard Dawkins' Perspective
Views Dollo's Law as a commentary on the improbability of retracing the same evolutionary path twice, irrespective of environmental conditions reverting.
Examples and Exceptions
Typical Example:
Human evolution: Current Homo sapiens cannot devolve into earlier forms like Dryopithecus or Ramapithecus.
Noted Exception:
Peppered Moth (Biston Betularia):
Historical Context:
Post-industrial revolution (19th century), increased pollution in Britain.
Survival Strategy:
Lighter moths (B. Betularia) became darker (B. Carbonaria) through industrial melanism to evade predators.
Reversal Evidence:
Late 20th century: Pollution reduction led to predator recognition of B. Carbonaria.
Result: Increase in lighter moth population, suggesting a reverse evolutionary trend, contrary to Dollo's Rule.
Significance
Dollo's Law remains a critical evolutionary principle, highlighting the general irreversibility of evolutionary processes, despite rare exceptions.
This arrangement places each image in a relevant section, providing visual representation for Richard Dawkins' interpretation of Dollo's Law and the Peppered Moth case study.
Cope's Rule by Edward Cope
Introduction to Cope's Rule
Edward Cope: Proposed the rule, though never formally stated; found implicitly in his writings.
Core Observations of Cope's Rule
Trend Toward Larger Body Size:
Animal groups often evolve toward increased body size over time.
Evidential Support:
Cope's argument backed by his studies in reptile and mammal phylogeny.
Noted increasing average body size through evolutionary time.
Relation to Lamarck's Proposition:
Echoes Lamarck's idea of organs' tendency to increase in size.
Examples
Animals:
Horses: Evolution from smaller Eohippus to larger modern Equus.
Plants:
Current herbs and shrubs developed from larger-sized trees.
Advantages of Larger Body Size in Animals
Enhanced Predation:
Better ability to capture prey.
Example: tigers, cheetahs.
Predator Avoidance:
Larger size aids in evading predators.
Example: giraffes, elephants.
Reproductive Benefits:
Increased body size correlates with greater reproductive potential.
Cognitive Development:
Brain size tends to increase with body size, potentially enhancing cognitive skills; evident in human evolution.
Bergmann’s Law Support:
Corroborates Cope's Rule.
States that average body size increases from equator to poles to conserve body heat.
Disadvantages of Larger Body Size in Animals
Resource Scarcity Challenges:
Larger animals face difficulties in areas with limited food resources.
Migration, a potential solution, is often not feasible for sizable animals like elephants.
Significance
Cope's Rule, despite its general nature, highlights significant trends in the evolutionary increase in body size, providing insight into both the advantages and potential limitations faced by organisms in different environments.
Gause's Rule by George Gause
Introduction
Originator: George Gause.
Also known as Gause's Competitive Exclusion Principle.
Key Concept: Two species competing for the same limiting resource cannot coexist at constant population values. When one species has even the slightest advantage or edge, the other will eventually be driven to extinction.
Evolution and Survival Mechanisms
Predatory Adaptations:
Development of offensive mechanisms, such as:
Larger body size.
Sharp canines.
Prey Adaptations:
Evolution of defensive mechanisms, including:
Enhanced speed.
Acute intelligence.
Purpose of Adaptations
To maintain ecological balance and reduce interspecies competition.
Principle of Competitive Exclusion
States: Ongoing competition cannot last indefinitely; it concludes with the exclusion of one or multiple species.
Role of Niches and Adaptation in Competition
Differentiating niches reduces competition.
Species may adapt to dominate competitors and avoid conflict.
Such adaptive strategies are central to Gause's Principle.
Gause's Principle or Competitive Exclusion Principle Explained
If two species:
Occupy identical ecological niches.
Compete for the same resources.
One will eventually drive the other to extinction.
Persistent competition necessitates niche differentiation, like resource partitioning strategies.
Conclusion
Competitive exclusion, though sometimes a slow process spanning centuries, is crucial for maintaining natural balance.
Significance
Gause's rule underscores the inevitability of competitive adaptations and the essential role of ecological niches in preserving biodiversity and ecological equilibrium.
Bergmann’s Rule by Carl Bergman
Introduction:
Bergmann's Rule, introduced by Carl Bergmann in 1847, addresses patterns in body size variations related to climatic variations.
It mainly applies to endothermic animals (those that produce their own body heat) like birds and mammals.
Rationale for the Rule:
Thermal Efficiency: Larger-bodied animals have a lower surface area relative to their volume. This means they radiate less body heat per unit of mass, which helps conserve heat in colder climates.
Heat Retention: A bulkier body, due to its reduced surface area-to-volume ratio, retains heat more efficiently than a smaller one. In cold environments, this can be a critical advantage.
Variations in Body Size:
From your notes: The average body size of organisms tends to increase from the equator to the poles. This can be seen in terms of volume, such as the subcutaneous layer or accumulation of fat.
Such variations are thought to be adaptations to local climates and serve to regulate the body temperature of the organism.
Examples & Evidence:
Observations have shown that species residing in colder climates, closer to the poles, are generally larger in size than their counterparts that live near the equator.
Polar bears, native to the Arctic region, are the largest bears, whereas the smaller sun bear is native to the tropical forests of Southeast Asia.
Exceptions & Criticisms:
While Bergmann's Rule is generally accepted, there are exceptions. Not all animals and birds show this trend.
Some researchers suggest that factors other than temperature, such as food availability or predation pressure, might also influence body size.
The rule's applicability may differ among different taxonomic groups or among populations of the same species.
Relation with Other Principles:
Bergmann’s Rule is similar in nature to other ecogeographical rules like Allen's rule, which states that animals in colder climates tend to have shorter limbs and appendages.
Conclusion:
Bergmann’s Rule offers an important lens to understand how species have adapted to their environments, especially concerning temperature variations. However, it's essential to approach it as a general principle with exceptions, considering the complexities of nature.
Mosaic Evolution by Gavin De Beer
Concept of Mosaic Evolution
Inconsistent and Asymmetrical Evolution: Highlights the non-uniform nature of evolutionary change across species.
Evolution, being gradual, doesn't occur uniformly or simultaneously in all aspects.
Varied Evolutionary Changes: Different parts or traits within a species may evolve in diverse manners.
Some body parts may evolve without corresponding changes in others.
Evolution may be rapid in one trait but slow in another.
Pace of evolution can fluctuate, being slow at certain times and rapid at others.
In rare cases, evolution might halt entirely.
Examples of Mosaic Evolution
Bipedal Locomotion in Human Evolution:
Demonstrates the non-synchronous nature of evolution within a species.
Emergence and modification of bipedal locomotion preceded changes in skull size and brain development.
Post bipedal evolution, both skull and brain experienced a rapid evolutionary phase, leading to modern humans.
African and Asian Elephants:
Shows variation in evolutionary trajectories between species.
African Elephants: Experienced simultaneous tooth modification and forehead shortening.
Asian Elephants: Underwent a rapid tooth modification followed by a later shortening of the forehead.
Conclusion
Natural Selection's Diverse Impacts:
Acts variably across different species.
Influences different body systems within the same species in diverse ways.
Exhibits geographical nuances in its operation.
The phenomena of mosaic evolution underscores the multifaceted and dynamic nature of natural selection, indicating its varied influence not only across different species but also within the same species on different bodily systems and in different geographical locales. This diversity in evolutionary paths emphasizes the complexity of biological evolution.
In evolutionary biology, Adaptive Convergence refers to a process where organisms, not closely related and evolving independently, develop similar traits.
This similarity arises due to exposure to analogous environmental conditions.
Scope and Application:
Convergence typically pertains to specific shared characteristics, not an organism's entire makeup.
Exemplification:
Case Study: Analogous Organs of Birds, Insects, & Bats.
These species possess differing anatomical structures but have evolved to perform the same function (i.e., flying).
Parallelism (Special Case of Convergence)
Definition and Relationship with AC:
Termed Parallel Evolution or Parallelism, this phenomenon is a distinct type of adaptive convergence.
Specifically encountered in closely related species.
Characteristics and Development:
Involves two evolutionary lines, both originating from similar ancestry, that evolve analogous features.
These lines evolve in tandem, paralleling each other, and often yielding similar outcomes or traits.
Exemplification:
Case Study: Running Habit in Equids.
Observable in the development of a running habit in species like horses, donkeys, and their relatives, despite each following separate evolutionary paths.
Difference Between Adaptive Divergence & Adaptive Convergence
Aspect
Adaptive Radiation/Divergence (AD-D)
Adaptive Convergence (AC-C)
Definition and Concept
- Known as Adaptive Radiation. <br> - Entails the evolution of diverse functional structures from a common ancestral form. <br> - Highlighted by the development of Homologous Organs.
- Refers to the independent evolution of similar traits in species not closely related due to analogous environmental conditions.
Key Process
- Rapid diversification into new forms from an ancestor species, especially during environmental changes, leading to the exploitation of new niches.
- Evolution towards similar traits despite different ancestral starting points, primarily because of similar environmental pressures.
Typical Examples
- Finches or Birds of the Galapagos Islands showcasing a variety of beak shapes and sizes to adapt to different food sources across various islands.
- Analogous organs like the wings of birds, insects, and bats, which, despite differing in structure, serve the same function (flying).
Primary Causes
- Often spurred by changes in geography or climate, or large-scale mutations leading to rapid speciation.
- Driven by similar environmental challenges necessitating specific functional traits for survival, regardless of differing ancestral lineages.
Characteristics
- Involves a common ancestry and the emergence of diverse phenotypes tailored to new or changing environments.
- Involves the development of similar traits in species from different lineages due to exposure to similar environmental conditions.
Nature of Organs Involved
- Homologous organs: Different functions evolved from a similar ancestral structure.
- Analogous organs: Similar functions evolved independently, usually not from a similar structure.
Relation to Environmental Change
- Phenotypic changes are directly correlated with environmental shifts, contributing to the survival and proliferation of species through new or modified traits.
- Similar traits develop in unrelated species predominantly because of similar environmental challenges, not because of a shared environment or ancestry.
How to Remember Analogous & Homologous Body Parts
Homologous Organs (related to Adaptive Radiation/Divergence):
"Same Origin, Different Function"
Think of the word "Homologous" as "Home" — it's like members of the same family (home) who start at the same point but end up with different professions (functions) as they grow. They have the same origin (home) but diverge in their roles (functions).
Example: The bones in a human's arm, a whale's flipper, a cat's leg, and a bat's wing look structurally similar and share a common ancestry, but they have evolved for different functions (grabbing, swimming, walking, flying).
Analogous Organs (related to Adaptive Convergence):
"Different Origin, Same Function"
"Analogous" can be thought of as "Analogy" — different things being used in similar ways. It's like people from different educational backgrounds (origins) ending up in the same job role (function) because they've developed similar skills independently.
Example: The wings of a bird, a bat, and an insect all serve the same function (flying) but are structurally different and don't come from a common ancestor.
Remember:
"Homologous" = "Home" = Same family (origin), different careers (functions).
"Analogous" = "Analogy" = Different histories (origins), same job (function).
✅Unit 9.1 : Human Genetics (Methods & Applications)
Methods
Methods for Study of Genetic Principles in Man Family Study
Pedigree Analysis
Introduction to Pedigree Analysis
Definition:
A classical technique in medical genetics, pedigree analysis involves creating detailed family trees using symbols to indicate individuals affected by genetic and other disorders, as described by the Anthropological Survey of India.
Purpose and Scope:
Serves as a comprehensive summary of inheritance patterns across generations, distinguishing modes of transmission for traits with similar phenotypes.
Facilitates the study of gene inheritance within families, clans, groups, etc.
Analyzes the presence or absence of specific traits or characters among family members, groups, or siblings.
Focuses on identifying patterns of inheritance for particular disorders or traits in families or races using various symbols and diagrams.
Symbols in Pedigree Analysis:
Key Representations:
Healthy individuals (Male/Female).
Adopted individuals (Male/Female).
Individuals with undesignated sex.
Marriage/Mating symbols, including consanguinous mating.
Indications of genetic disorders in males and females.
Carrier females (specifically for genetic disorders).
Representation of marriage and offspring.
Siblings.
Exceptions: Males cannot be carriers of X chromosome-linked disorders but can carry autosomal disorders.
Distinction between monozygotic (identical) and dizygotic (fraternal) twins.
Applications of Pedigree Analysis:
Criss Cross Inheritance:
Allows detailed study of traits transmitted from father to daughter and mother to son.
Population Studies:
Critical in researching character occurrence, disorder transmission, and character suppression within a population.
Autosomal Dominant Disorders:
For example, Huntington’s Disease (also known as Korea).
Autosomal Recessive Inheritance:
Disorders like Phenylketonuria can be identified.
Genetic Processes:
Enhances the study of genetic counseling, screening, and imprinting related to human diseases.
Preventive Measures:
Increasingly utilized before marriages to control the propagation of genetic disorders in future generations.
Twin Study: Detailed Notes
Overview
Twin Studies are pivotal in understanding human behavior and genetics.
They primarily involve the Co-Twin Controlled Method.
Types of Twins
2.1. Monozygotic Twins (Identical Twins)
- Originate from one zygote that splits into two.
- These twins are always of the same sex.
- They are identical genetically.
- Frequency: Occur in 3 to 4 per 1000 live births globally.
- Noteworthy for their striking physical resemblance.
2.2. Dizygotic Twins (Fraternal Twins)
- Result from the fertilization of two different eggs by two different sperms.
- Essentially siblings born at the same time.
- Not genetically identical.
- Frequency: Varies significantly among populations.
- Example: 6 to 8 per 1000 live births in South Asian populations.
- Up to 40 per 1000 live births in African populations.
- Higher likelihood in specific demographics:
- Older mothers (four times more likely).
- Taller and heavier women.
- Those with a family history of twins.
- Smokers.
ACE Model in Genetic Studies
Utilized extensively in twin studies.
ACE is an acronym for:
3.1. A: Additive genetic effects.
3.2. C: Common environmental factors and heritability.
3.3. E: Environmental factors unique to the individual.
Significance of the ACE Model Studies
Based on extensive case works analyzing thousands of twin families.
Outcomes underscore the critical role of genetic factors.
Genes significantly influence behavior and IQ levels in both identical and non-identical twins.
Exposure to various environments shapes the twins' behavior uniquely.
Similar environments often lead to similar behaviors, whereas different environments can lead to divergences.
Twin studies, incorporating both identical and non-identical twins, are invaluable for:
Examining the influence of genetics and environment.
Studying various traits, disorders, and phenotypes.
Key Insights:
Genetics play a substantial role in determining behavior and physical attributes.
The environment also has a profound impact, capable of shaping individual behavior even in genetically identical individuals.
Twin studies are a powerful tool for disentangling these effects and understanding human biology and behavior.
Co-Twin Control Method: In-Depth Analysis
Introduction
The Co-Twin Control Method is a specialized technique within twin studies.
Focuses predominantly on monozygotic twins under controlled environmental conditions.
Historical Background
Arnold Gesell, a pioneering geneticist, was the first to utilize this method.
Purpose: Investigating behavior and early development in identical twins.
Methodology
Involves distinct treatment of each twin:
One receives specific treatment or exposure to environmental conditions concerning a trait.
The other serves as a control, without the particular environmental exposure.
Designed to isolate the effects of environment versus genetics on development.
Gesell's Observations
Identical twins exhibit substantial physical and behavioral similarities.
Case Study: Around the age of 42 to 46 weeks, neither twin could climb stairs.
One twin underwent six months of training and encouragement, subsequently able to climb stairs.
The control twin, unexposed to training, initially feared climbing.
Remarkably, after spending one to two weeks with the trained sibling, the control twin also began climbing with minimal training.
Conclusions from Gesell's Studies
Repetition of these results in multiple studies affirmed Gesell's findings.
Demonstrated that physical training enhances skills, potentially appearing earlier due to genetic similarities.
However, even with less training, similar outcomes are achievable due to identical genetics.
The studies highlighted the nuanced impacts of both genetic and environmental factors on development.
Significance of Co-Twin Control Studies
Provides a more refined analysis of the relative impacts of genetics versus environment.
Enhances understanding of behavioral and physical development.
Offers insights into how identical genetics respond under different environmental conditions and stimuli.
Key Insight:
Co-twin control studies underscore the complex interplay between genetics and environment, even in individuals with identical genetic makeup. They are crucial for disentangling genetic and environmental influences on various traits and behaviors.
Foster Child Studies
Definition & Importance:
Complementary to twin and co-twin controlled methods, focusing on nature and nurture.
Aim to discern genetic principles based on environmental conditions.
Major focus areas: mental traits, cognitive skills, psychological development.
Methodology:
Random selection of children ensures equal distribution of genetic factors (e.g., intelligence, IQ).
Placement in various homes studies the effects of different environments.
Key Studies:
Chicago Study:
Notable for greatly minimized sample selection bias.
Findings: Direct proportionality between the quality of adoptive homes and children’s IQ scores.
Higher IQ in affluent families.
Average IQ in moderate-income households.
Lower IQ in less affluent families.
Conclusion: Environment significantly impacts IQ and mental development.
Minnesota Graded Homes Study:
Involved reversing the living conditions of affluent and labor-class children.
Findings:
Affluent children retained higher IQs even in labor-class homes.
IQ improvements in labor-class children raised in affluent homes.
Conclusion: Both genetics and environment influence mental makeup, intelligence, and psychological development.
Challenges & Criticisms:
Issue: Inherent biases and errors due to non-random, choice-based child selection.
Solution: Improvements proposed by Osborne.
Key Suggestions:
Early placement in adoptive homes, minimizing influence from original environment.
Maximized randomness in child selection, minimizing selective placement.
Exposure of same class children to similar conditions, including same ethnicity and race, ensuring consistent environmental variables
Cytogenetic Method
Definition & Scope:
Cytogenetics: The study of chromosomes and genetic traits within cells.
Contributes to understanding the human genome organization and related changes.
Correlates phenotypic differences with chromosomal abnormalities, focusing on changes in chromosome number and structure.
Key Approaches/Methods:
Barr Body Analysis:
Barr Body: Condensed chromatin from one X chromosome, visible in the cell nuclei of females.
Originates from one of the two X chromosomes, specifically the inactive one.
Indicator of the number of X chromosomes (number of Barr bodies is one less than the number of X chromosomes).
Key Identifiers:
Healthy females: One Barr body.
Healthy males: No Barr body.
Applications:
Early detection of chromosomal disorders like Klinefelter's (XXY) and Turner’s (XO) syndromes.
Klinefelter's: Presence of an extra X chromosome (XXY).
Turner’s: Absence of one X chromosome (XO).
Used in 1968 Olympics to identify male athletes posing as females.
Mechanism:
Females have two X chromosomes, one from each parent.
One X chromosome becomes inactive during early developmental stages.
X inactivation is random and happens individually in cells.
Different cells might inactivate either the paternal or maternal X chromosome.
Significance:
A crucial tool in genetic studies.
Enables early disorder detection, reducing disease severity and time for intervention.
Chromosomal & Karyotype Analysis
Overview
Karyotyping:
Represents chromosomes pictorially.
Assesses structures, features, or abnormalities in chromosomes.
Importance:
Vital in genetic mapping.
Crucial for studying genetic imprints in diseases.
Prime research area in molecular diagnostics.
Cell Type for Karyotyping
Commonly performed on White Blood Cells (WBCs).
Rationale: Mature Red Blood Cells (RBCs) lack a nucleus, whereas WBCs contain nuclei, essential for chromosomal study.
Procedure
Chromosomes are:
Isolated.
Stained with dyes.
Rearranged based on size and shape.
Objective: Identify various chromosome forms, including:
Telocentric
Acrocentric
Metacentric
Submetacentric
Chromosomal Banding Techniques
Crucial for revealing the characteristic dark and light band patterns on chromosomes.
Types:
G Banding (Giemsa)
Most prevalent method.
Utilizes Giemsa dye.
Achieves distinctive banding patterns.
Q Banding (Quinacrine)
R Banding (Reverse)
Involves:
Denaturation of chromosomes and proteins through heating.
Staining with Giemsa.
Purpose: Analyze chromosome size and shape.
C Banding (Centromeric)
Specifically stains the heterochromatin.
Targets non-coding regions of the chromosome.
Advanced Techniques
Spectral Karyotyping:
Innovative cytogenetic method.
Features:
Less time-consuming.
Eliminates the need for multiple banding techniques.
Allows simultaneous visualization of all 23 chromosome pairs in different colors.
Technological Impact
Ultraviolet Fluorescent Technique: Employed in certain banding processes.
Spectral karyotyping and other advancements have significantly streamlined chromosome analysis.
Significance in Medical Science
Chromosomal banding and karyotyping remain extensively used for:
Genetic mapping.
Investigating genetic roles in diseases.
Their ongoing development continues to be a key focus in molecular diagnostics.
Chromosomal & Karyo Type Analysis
Chromosomal bending technique and Karyotypic
Karyotyping is pictorial presentation of chromosomes by segregating
them to study the features, structures or abnormalities in the structure
and function of chromosomes
Mature form of RBCs does not have a nucleus. Most often karyotyping is done based on WBCs. Becoz WBCs have nucleus.
In karyotyping the chromosome Is isolated trained with some dye and is rearranged based on size and shape to get a hind about Telocentric,
Acrocentric, metacentric and submetacentric forms of chromosomes.
4 different types of bending technique.
G bending,Geimsa – name of the dye
Is the most common method of bending in which staining with
geimsa dye will mark chromosomes with a typical dark and light band
patterns.
Ultraviolent Flurocent technique is being used
Q bending,Quinacrine
R bending -Reverse
Chromosomes and proteins are denatured with heating and then
stemmed with geimsa to study their size and shape
C bending-centromeric
Only the heterochromatin (non coding) part of chromosome is
strained
With advancements Spectral karyotyping is being used which is a cytogenetic method,less time consuming ,not involving different different bending techniques and can be used to simultaneously see all 23 pairs of chromosomes with different colors.
Chromosomal bending techniques are one of the most widely used method in genetic mapping and to study genetic imprints in disease. and is one of the prime research areas in molecular diagnostics today
Bio Chemical Methods for Genetic Studies
Introduction
Objective:
Study cellular and subcellular biomolecules.
Focus on genetic chemical compounds (DNA, RNA, proteins).
Analyze functioning of biomolecules within cells.
Significance:
Essential for understanding gene activities and biochemical analysis of gene-controlled reactions.
Types of Biomolecules
Produced by cells:
Lipids
Nucleic acids
Proteins
Carbohydrates
Enzymes
Techniques Used
Chromatography:
Principle: Separation based on color, hydrophilic, and hydrophobic properties.
Function: Filters various biomolecules.
Gel Electrophoresis:
Utilized in genetic engineering and recombinant DNA technology.
Principle: Separates charged molecules (DNA, RNA, proteins) based on size and charge.
Process: Involves passing a small-grade electric current through a gel containing these molecules.
Purpose of both techniques:
Distinguish inherited differences in biomolecule structure and function.
Reveal activities of genes within cells.
Advanced Diagnostics
Enhancements in genomics and biochemical studies have led to numerous diagnostic tests, including:
Polymerase Chain Reaction (PCR): Amplifies DNA segments.
ELISA (Enzyme-Linked Immunosorbent Assay):
Based on antigen-antibody reactions.
Detects various conditions, including infections (HIV, hepatitis) and genetic mutations in cancer.
Importance in Genetic Studies
These biochemical methods:
Provide insights into the intricate functions of cellular/subcellular components.
Are critical for diagnosing diseases, studying genetic variations, and understanding biological functions at a molecular level.
Current Trends and Future Applications
Ongoing advancements continue to refine these techniques, expanding their applications in medical diagnostics and genetic research.
Immunological Methods
Introduction to Immunogenetics:
Definition: Focuses on the genes and proteins that control the immune response.
Function: Governs the ability of body cells to combat pathogens, allergens, etc., through the secretion of specific chemicals and proteins safeguarding the body cells.
Immuno-globulins (Ig): Essential components that structure, function, and regulate the cellular control of the body's immune response.
Antigen-Antibody Reaction: The variability in antibody responses to different antigens is central to immunological methods.
Diagrammatic Representation: (place the diagram here)
Importance of Understanding Antibodies:
Biosynthesis and Structure: Critical for the detection, diagnosis, and treatment methodologies utilizing antibodies.
Applications:
Blood group determinations.
Facilitation of blood transfusions.
Organ transplant compatibility assessments.
Rhesus (Rh) factor incompatibility in childbirth.
Applications of Immunogenetic Methods:
ELISA Test: Utilizes antigen-antibody reactions.
Interferons: Antiviral glycoproteins formed by various body cells in response to viral exposure.
Function: Produced primarily by blood cells, they combat viral infections.
Immune System Functioning:
Genetic Principles: Underlie the functioning of the immune system.
Types of Immunity:
Cell-Mediated Immunity:
Regulation: Controlled by cells, specifically white blood cells (WBCs) or leucocytes.
Key Players: B cells and T cells.
Subtypes of Leucocytes: Lymphocytes and monocytes.
HIV/AIDS: Reduction in CD4 lymphocytes when HIV progresses to AIDS.
Cell Types:
Helper cells.
Memory cells.
Antigens: Invaders triggering immune responses; can be allergens, pathogens, or even dust particles.
Antibodies: Defense proteins produced against antigens.
Isoagglutinogens: Various forms including IgA (in body fluids), IgD, IgE (allergic reactions), and IgG (can cross the placenta).
Key Terms Highlighted:
Immunogenetics
Immuno-globulins (Ig)
Antigen-Antibody Reaction
Biosynthesis
ELISA Test
Interferons
Cell-Mediated Immunity
Leucocytes
Antigens
Antibodies
Isoagglutinogens
Important Concepts:
The specific response of body cells to various external invasions through a complex system of proteins and chemicals.
The necessity of understanding the biosynthesis and structure of antibodies for medical applications.
The role of genetic principles in the functioning of the immune system.
The diversity and functionality of different cells and proteins in maintaining immunity.
Applications
DNA Technology & Recombinant Technologies
Biotechnology
Definition
Biotechnology refers to technological interventions in living beings, encompassing modifications in their genetic material and enzymes. The primary purpose is to create products and processes beneficial for mankind.
BT-Cotton: Genetically modified to be resistant to pests.
BT-Brinjal: Altered for improved pest resistance.
GM-Mustard (Hybrid mustard DMH-11): Developed for enhanced pest resistance.
Biofortified Wheat: Fortified to increase nutritional value and pest resistance.
Golden Rice: Genetically enhanced to increase vitamin A content (Note: Mention of groundnut-GJ, the largest producer, seems misplaced here and might pertain to another context).
Flavr Savr Tomato: Engineered for longer shelf life by suppressing polygalacturonase enzyme, hence preventing the softening of the outer covering (no taste or nutritional value alteration).
Nematode-Resistant Tobacco: Modified for increased resistance to nematodes.
Aflatoxin-Resistant Groundnut: Engineered to resist aflatoxin (a toxin released by the Aspergillus fungus colony).
Health and Medicine
Genetically Engineered Insulin: Recombinant DNA technology used to produce human insulin.
Genetically Engineered Steroids: Steroids produced using genetic engineering for various medical applications.
Genetically Engineered Vaccines: Vaccines developed using biotechnological methods for increased efficacy and safety.
Stem Cell Therapy: Use of stem cells to treat or prevent diseases.
DNA Fingerprinting/Profiling/Mapping: Techniques for identifying the genetic makeup of individuals.
Molecular Diagnosis:
PCR (Polymerase Chain Reaction): Technique to amplify a single or few copies of a piece of DNA.
ELISA (Enzyme-Linked Immunosorbent Assay): Test that uses antibodies and color change to identify a substance.
Blotting Techniques: Molecular biology techniques (northern, southern, western) to identify specific DNA, RNA, and proteins.
Mitochondrial Replacement Therapy: Technique producing a "three-parent baby" to prevent mitochondrial diseases.
CRISPR-Cas9: A revolutionary genome-editing technology.
Gene Therapy: Treatment of disease by modifying genes.
Gene Silencing:
Broadly, Genetic Engineering is about gene modification.
Objectives:
Introduce a new trait.
Suppress an unwanted trait (e.g., using RNA interference technology in the Flavr Savr Tomato to inhibit the polygalacturonase enzyme, preventing outer covering softening).
Note: Genetic Engineering often involves Recombinant DNA Technology; these terms are sometimes used interchangeably.
RNAi (RNA interference), also known as antisense technology, is a form of gene silencing.
Recombinant DNA Technology (rDNA or rDNAt)
Overview
Recombinant DNA Technology involves combining genetic material from multiple sources, creating sequences that would not otherwise be found in the genome. It's pivotal in genetic engineering and genome editing.
Process and Application
Plasmid Use: Plasmids, often used as vectors, transfer cut DNA segments from a source genome (e.g., Bacteria BT genes) to a target genome (e.g., Cotton).
BT Genes: Cry genes, responsible for producing the toxin thurioside, are introduced into host plants using a bacterium's plasmid.
Plasmid Types:
In agricultural biotech, plasmids from Agrobacterium (known as Ti plasmids - tumor-inducing due to their effect on broadleaf plants like tobacco, soybean, tomato, etc.) are utilized.
In health-related biotech, plasmids from E. coli bacteria are commonly used.
Common Method: rDNA technology is widely used for gene modifications, crucial in genetic engineering and genome editing practices.
BT Cotton: A variety of cotton genetically engineered to be resistant to pests, specifically through the introduction of Bacillus thuringiensis (BT) genes.
Agricultural Challenges: Issues such as bollworms, beetles, and cotton worms pose significant threats to cotton production.
Tools of Recombinant DNA Technology
Enzymes: Specialized molecules that cut and splice DNA strands at specific sequences, enabling the insertion or modification of genes within a DNA sequence.
Cloning Vectors: DNA molecules originating from viruses, plasmids, or the cells of higher organisms that can replicate foreign DNA fragments when introduced into a host organism.
Competent Host: Organisms, often bacteria like E. coli, that can accept, take up, and express foreign DNA, allowing for the replication of the introduced DNA sequence and production of desired products.
CRISPR Cas 9
CRISPR-Cas9
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and Cas9 (CRISPR-associated protein 9) together form a system that allows for precise genetic editing. It was adapted from a naturally occurring genome editing system in bacteria, which use CRISPR-derived RNA and various Cas proteins, including Cas9, to fend off attacking viruses. The modified version of this system has been engineered to edit the genomes of higher organisms, including humans.
Key Concept
The key concept behind CRISPR-Cas9 is its ability to find a specific bit of DNA inside a cell and cut it at a precise spot. The system works by utilizing a piece of RNA with a matching sequence to the target DNA, which guides the Cas9 enzyme to the right point in the genome. This ensures that the Cas9 enzyme cuts DNA at the right point, which can disable a gene or allow for a new one to be inserted.
Process
Design: Scientists design a piece of RNA called "guide RNA" (gRNA) that matches the sequence of a target gene in the DNA that they wish to modify.
Combination: The gRNA combines with the Cas9 protein.
Binding and Cutting: The gRNA guides the Cas9 complex to the target site in the genome, where Cas9 binds and cuts the DNA at the exact spot that matches the code in the gRNA.
Editing: Once the DNA is cut, the cell tries to repair the break using its repair mechanisms. In doing so, it can introduce or remove genetic material, or the repair can be “hijacked” by scientists who introduce a desired sequence for integrating into the genome.
Potential Applications of CRISPR-Cas9
Treatment of Neural Disorders: By targeting the genetic roots of diseases like Parkinson’s and Alzheimer’s, scientists could potentially correct the mutations causing these diseases or modify neural pathways to alleviate symptoms or slow progression.
Correcting Congenital Heart Defects (CHD): By editing the DNA of embryos or even adult patients, it might be possible to correct the genetic defects that cause congenital heart issues.
Cancer Treatment: CRISPR can be used to modify immune cells to fight cancer more effectively, target and destroy cancerous cells, or edit out genetic mutations that increase the risk of cancer.
Gene and Stem Cell Therapy Support: CRISPR can enhance the effectiveness of gene therapy and stem cell therapy by increasing precision in the genetic material that is introduced into the cells or the patient.
Regenerative Medicine: By influencing cell differentiation pathways, CRISPR could potentially regenerate tissues damaged by spinal cord injuries, arthritis, etc.
Enhanced Immunotherapy: Post cancer treatment, CRISPR can be used to modify immune cells to prevent recurrence and improve the body’s resistance to cancer.
Ethical Considerations and Challenges
While CRISPR-Cas9 technology has opened many doors in genetic medicine and research, it also comes with ethical challenges. These include concerns over human germline editing, off-target effects (unintended genetic modifications), and equitable access to therapies derived from the technology. Moreover, there is a need for comprehensive clinical trials to establish the safety and efficacy of these interventions in humans.
Regulatory Oversight
Given its potential for significant impact, CRISPR-Cas9 is subject to regulatory scrutiny. Agencies like the U.S. Food and Drug Administration (FDA) and similar bodies worldwide have guidelines for gene therapy and genetically modified organisms (GMOs), which CRISPR is often subject to. The evolving nature of the technology also means that regulatory frameworks need to be continuously updated.
Gene Therapy
Introduction
Definition: Gene therapy involves the use of genetic engineering and modifications to correct defective genes responsible for disease development.
Aim: To replace a faulty gene with a healthy, functional one or repair a damaged gene to restore its functionality.
Method: This can involve direct correction of the gene or introducing a new gene, a process known as gene augmentation therapy.
Applications and History
Focus: Mainly targets gene defects identified during early developmental stages.
Milestone: The 1st successful gene therapy was conducted for ADA deficiency.
ADA Deficiency: A lack of the enzyme Adenosine Deaminase, crucial for a functional immune system.
Current Status: Still in preliminary phases of research and development.
Limitations: High costs restrict its widespread application.
Potential Uses: Could treat genetic disorders such as haemophilia, cystic fibrosis, and SCID (Severe Combined Immune Deficiency).
Types of Gene Therapy
Somatic Gene Therapy: Targets somatic cells (non-reproductive cells). Changes affect only the individual and are not passed to offspring.
Germ Line Gene Therapy: Involves modifications to the germ cells (sperm or egg).
Inheritance: Changes will be inherited by the next generation.
Challenges
Primary Concern: The utilization of bacteriophages as the prevalent vector poses significant risks.
Issue: Bacteriophages are a type of virus that can potentially initiate a pathogenic response, representing one of gene therapy's largest hurdles.
3 Parent Baby: A concept due to the involvement of three genetic contributors.
Legal Status:
UK: First country to legalize mitochondrial gene therapy.
India: Has not legalized this therapy yet.
Purpose:
Allows couples with rare mitochondrial genetic disorders to have healthy babies.
Achieved through the replacement of faulty mitochondria with healthy ones from a donor's egg.
Mitochondrial Disorders:
Examples include Barth’s syndrome, Leigh’s syndrome, etc.
Caused by faulty mitochondrial genes in the mother’s egg.
Can be transmitted to the next generation due to the maternal inheritance of mitochondrial genes.
Procedure:
The nucleus is removed from the healthy donor mother’s egg to create an enucleated egg, ensuring it contains healthy mitochondria.
The nucleus from the biological mother’s egg is then transplanted into the enucleated egg of the donor mother.
This egg now carries chromosomal DNA from the biological mother and mitochondrial DNA from the donor mother.
The modified egg is fertilized with the biological father’s sperm to form a healthy zygote.
The resulting child has genetic information from three individuals:
Chromosomal DNA from both biological parents.
Mitochondrial DNA from the donor mother.
Therapies Used for Mitochondrial Gene Replacement:
Pronuclear Transfer: One type of MRT where the mother's and father's nuclear DNA is transferred to a donor egg with healthy mitochondria which has had its own nucleus removed.
Maternal Spindle Transfer: Another method where the spindle chromosomes from the mother’s egg are transferred to a donor egg that had its nucleus removed.
Polar Body Genome Transfer: A third method currently under research.
Important Terms:
Enucleated Egg: An egg cell that has had its nucleus removed.
Mitochondrial DNA (mtDNA): Genetic information found in the mitochondria, usually inherited maternally.
Zygote: The cell formed by the fertilization of an egg by a sperm, which eventually develops into an embryo.
Uniparental Disomy (UPD) & Genomic Imprinting:
Overview:
Uniparental Disomy (UPD): A genetic event where an individual receives two copies of a chromosome, or part of a chromosome, from one parent and no copies from the other parent.
Genomic Imprinting: A genetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner.
Occurrence and Impact:
UPD is a random phenomenon.
Often, UPD may not adversely affect health or development because most genes are not imprinted.
However, in cases where imprinted genes are involved, UPD can lead to various health challenges and developmental delays.
Association with Disorders:
Certain abnormalities, although not life-threatening, can occur due to the interaction between UPD and genomic imprinting.
Well-known Conditions Associated with UPD:
Prader-Willi Syndrome:
Characterized by uncontrolled eating and obesity due to the lack of satiety.
Angelman Syndrome:
Leads to intellectual disability and impaired speech.
These conditions are caused by UPD involving imprinted genes on chromosome 15.
Important Terms:
Uniparental Disomy (UPD): The inheritance of two copies of a chromosome from one parent.
Genomic Imprinting: The expression of gene alleles depending on the parent they were inherited from, which can lead to unique syndromes when disrupted.
✅Unit 9.2 : Different Topics under the heading
Mendelian Genetic in Man Family Study
Mendelianism & Human Genetics(2 Ques out of 10 Markers Asked in 2022)
Background:
Gregor Johann Mendel: An Austrian monk and philosopher turned geneticist, recognized as the "Father of Genetics".
Genetics: The science of heredity and variation in living organisms.
Heredity: The transmission of traits from parents to their offspring.
Mendel's Experiments:
Studied seven distinct traits of the garden pea (Pisum sativum).
Proposed that traits are determined by "factors" (now known as genes).
Identified the concepts of "dominant" and "recessive" traits.
Pea Plant Traits Studied by Mendel:
Stem Height: Tall (dominant) vs Dwarf (recessive).
Seed Shape: Round (dominant) vs Wrinkled (recessive).
Seed Color: Yellow (dominant) vs Green (recessive).
Flower Color: Purple (dominant) vs White (recessive).
Flower Position: Axial (dominant) vs Terminal (recessive).
Pod Shape: Inflated (dominant) vs Constricted (recessive).
Pod Color: Green (dominant) vs Yellow (recessive).
Mendelianism:
Based on monohybrid and dihybrid crosses among various traits in organisms.
Monohybrid Cross: Involves the study of one character at a time.
Dihybrid Cross: Involves the study of two characters simultaneously.
Mendel's Observations on Heredity:
Traits are controlled by unit factors (genes), existing in pairs in organisms.
These pairs can be in a homozygous (pure) or heterozygous (mixed) condition.
Example:
Tall (TT) - Homozygous dominant.
Dwarf (tt) - Homozygous recessive.
Hybrid Tall (Tt) - Heterozygous.
Mendel’s Three Laws:
Law of Dominance: In a heterozygote, one trait will conceal the presence of another.
Law of Segregation (First Law): Alleles segregate independently during gamete formation; each gamete carries only one allele for each trait.
Law of Independent Assortment (Second Law): Genes for different traits assort independently of one another during gamete formation.
Important Terms:
Dominant: A trait that is phenotypically expressed in heterozygotes.
Recessive: A trait that is phenotypically expressed only when two recessive alleles are present.
Homozygous: Having two identical alleles for a particular gene.
Heterozygous: Having two different alleles for a particular gene.
Monohybrid Cross: A cross between parents differing in only one trait.
Dihybrid Cross: A cross between parents differing in two traits.
Exception to Mendelianism
Co-Dominance
Definition: A genetic scenario where both alleles are dominant together.
In a heterozygous condition, both alleles of the gene express themselves simultaneously.
This expression shows no typical dominant-recessive relationship.
There's no intermediate result; the traits are expressed independently.
Examples and Exceptions:
The primary example is the ABO blood group system in humans, specifically the AB blood group.
AB blood group:
Features isoagglutinogens (protein-based substances).
These are exceptions to Mendel's laws (referred to as "Mendel exceptions").
Diagrammatic Representation: Depicts how both alleles express themselves without blending or one being recessive.
Important Terms Highlighted:
Co-Dominance: A form of dominance wherein the alleles of a gene pair in a heterozygote are fully expressed. This results in offspring with a phenotype that is neither dominant nor recessive.
Heterozygous Condition: Refers to having inherited different forms of a particular gene from each parent.
ABO Blood Group System: A classification system for the antigens of human blood, used in blood transfusion therapy, and includes groups A, B, AB, and O.
Isoagglutinogens: Substances which cause agglutination (clumping) of cells or particles, specifically in the context of blood groups.
Mendel's Laws/Mendel Exceptions: The principles of heredity formulated by Gregor Mendel, based on his work with pea plants. Exceptions refer to phenomena that don't adhere strictly to these basic laws, indicating the complexity of genetic inheritance.
Incomplete Dominance
Definition: A genetic phenomenon where the dominant allele is not entirely dominant over the recessive allele.
The effect of one allele is more pronounced (dominant), yet it doesn't completely mask the presence of the recessive allele.
The outcome is an intermediate blend of the two alleles, rather than one trait being clearly dominant over the other.
Characteristics and Occurrence:
This phenomenon is less common in humans; it is primarily observed in plants.
The resultant phenotype is a mix or blend of the parent phenotypes.
Examples:
Average Height in Humans:
When alleles for height exhibit incomplete dominance, individuals of average height are the result of the blending of alleles for tall and short stature.
Pink Roses in Botany:
The occurrence of pink roses is a classic example of incomplete dominance.
Red and white roses cross-pollinate to produce pink roses, indicating a blending of the two colors, rather than one being completely dominant.
Important Terms Highlighted:
Incomplete Dominance: A genetic condition in which the phenotype of the heterozygote lies somewhere between the phenotypes of the two homozygotes; neither allele is completely dominant or completely recessive.
Dominant Allele: An allele that expresses its phenotypic effect even when heterozygous with a recessive allele; it masks the expression of the recessive allele.
Recessive Allele: An allele that produces its characteristic phenotype only when its paired allele is identical.
Phenotype: The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
Average Height in Humans: Refers to a trait influenced by multiple genes, and when discussing incomplete dominance, it is a simplified representation of the blending of "tall" and "short" alleles.
Pink Roses in Botany: An example of how incomplete dominance can result in a new phenotype (pink) from the parents (red and white) that is intermediate, not a mix, of the two original traits.
Definition: A type of genetic inheritance where traits are determined by more than two genes (referred to as polygenes or polyfactors).
It's not just a single gene dictating a trait, but multiple genes collectively influencing the outcome.
Characteristics:
The expression of traits is the collective result of the interaction of these genes.
Polygenic inheritance can be seen as an extension of incomplete dominance.
It results in many possible phenotypes due to the influence and inter-reaction of multiple alleles through an additive effect.
Human Traits:
Several characteristics in humans are polygenic, including:
Skin color: Influenced by more than three genes.
Eye color: Considered to be regulated by as many as 16 different genes.
Hair color.
Height: Polygenic inheritance is evident, with no dominant or recessive trait expressed in the majority of the population.
Diagrammatic Representation: Shows the spectrum of possible phenotypes resulting from polygenic inheritance.
Important Terms Highlighted:
Polygenic Inheritance/Multifactor Inheritance/Quantitative Inheritance: These terms refer to the genetic process where multiple genes affect a complex trait.
Polygenes/Polyfactors: Multiple genes that contribute to the overall phenotype of a particular trait.
Additive Effect: In genetics, this refers to the cumulative effect of different genes on a single phenotype.
Phenotype: The observable physical properties of an organism; these include the organism's appearance, development, and behavior.
Skin Color, Eye Color, Hair Color, Height in Humans: Examples of polygenic traits, meaning they are controlled by more than one gene, and each gene might have two or more alleles. This complexity leads to a continuous variation of phenotypes.
Genetic Polymorphism / Multiple Allelism
In Unit 9.3
Definition:
Genetic Polymorphism: Refers to the simultaneous occurrence of two or more discrete phenotypes within a population. A condition where a trait in a population is controlled by multiple alleles (an extension of Mendel's law).
Multiple Allelism: Occurs when there are more than two alleles within a population that determine a specific trait.
Characteristics:
These genetic conditions contribute to the diversity of a population, allowing for various expressions of a trait.
The term "polymorphous" implies multiple forms or looks.
Importance in Genetics:
Polymorphism and multiple allelism are crucial for understanding the genetic complexity and variability within populations.
They explain the genetic basis of variations and adaptations that occur in populations.
Examples in Humans:
A classic example of multiple allelism is the ABO blood group system.
Other examples might include traits like hair color and eye color, where several forms exist within a population due to multiple alleles influencing these traits.
Important Terms Highlighted:
Genetic Polymorphism: The occurrence of different forms or types in individual organisms or among organisms of the same species, independent of age, sex, or environment. In genetics, this refers to the occurrence of several different phenotypes in a population.
Multiple Allelism: The existence of more than two alleles at a locus within a population; it's an extension of the Mendelian concept of biallelic systems, showcasing even more genetic diversity.
Phenotype: The set of observable characteristics of an individual organism resulting from the interaction of its genotype with the environment.
ABO Blood Group System: A system of blood classification based on the presence or absence of inherited antigenic substances on the surface of red blood cells; a classic example of a trait determined by multiple alleles.
Single Factor
In genetics, a single factor refers to a scenario where a single gene or genetic locus is responsible for a particular trait or condition. Each gene might have different forms, known as alleles, which can result in variations in the trait among individuals.
Multi Factor
Multi-factor, or multifactorial inheritance, refers to the type of genetic inheritance where multiple genes, often along with environmental factors, contribute to the expression of a particular trait or the occurrence of a particular condition. This form of inheritance is typical for complex traits and diseases like heart disease, diabetes, and obesity.
Lethal Genes
Lethal genes are genes that, when expressed in a certain way, lead to the death of the organism. They can be dominant or recessive.
For example, in a homozygous condition, a recessive lethal allele would cause lethality, whereas a dominant lethal allele would cause lethality even in a heterozygous condition.
Sub Lethal Genes
Sub lethal genes are those that cause significant harm or disadvantage to an organism but do not cause death. They may result in severe developmental disorders, diseases, or other detrimental conditions that reduce the fitness of the individual.
Polygenic Inheritance in Man
Polygenic inheritance refers to the inheritance of traits that are determined by more than one gene. These genes, often located at different loci on different chromosomes, contribute to a single trait. In humans, many traits such as height, skin color, and intelligence are thought to be influenced by polygenic inheritance. Each gene contributes a small amount to the expression of the trait, and the combined effect of many genes, often in interaction with environmental factors, results in the continuous variation observed for these traits. This type of inheritance results in a bell-curve distribution of traits within a population, where most individuals have an intermediate trait value while only a few have extreme values.
✅Unit 9.3 : Different Topics under the heading
Concept of Genetic Polymorphism & Selection
Genetic Polymorphism
Refined Definition:
Genetic polymorphism refers to the occurrence of more than one form or morphology (morph) in a population.
A critical criterion is that the least common form (rare allele) must have a frequency of more than 1% in the population.
Frequency and Natural Selection:
To be classified as a genetic polymorphism, a minimum frequency of 1% is required for the character/trait in question.
A frequency below 1% signifies only those recurrent mutations that occur randomly and are not selected by nature.
In contrast, a frequency above 1% indicates a polymorph, signifying genetic combinations that arise due to recurrent mutations plus natural selection.
Expression in Populations:
The expression of genetic polymorphism in a specific population, following natural selection, becomes visible only after several generations.
Levels of Occurrence:
Genetic polymorphism is not confined only to genes.
It can also occur at various biological levels, including:
The cell surface.
The chromosomal level, which may involve coding or non-coding regions.
Important Terms Highlighted:
Genetic Polymorphism: A phenomenon where more than one form or "morph" of an individual exists in a population, and the frequency of the least common morph exceeds 1%. It reflects the genetic diversity of a population.
Frequency in Population Genetics: Refers to the occurrence of a specific form or trait in a population, critical for understanding the dynamics of genetic polymorphism.
Natural Selection: The process through which traits become more or less common in a population due to consistent effects upon the survival or reproduction of their bearers. It is a key mechanism of evolution.
Generations in Population Genetics: Refers to the time span between the birth of individuals and the birth of their offspring, used as a measure in the study of genetic changes over time.
Cell Surface and Chromosomal Level Polymorphism: Indicates that genetic variability is not restricted to the genetic code itself but extends to various physical manifestations at the cellular and chromosomal levels.
There are Two Types of Genetic Polymorphism
1. Balanced Polymorphism / Heterozygous Advantage
Definition:
Balanced Polymorphism: A stable condition where substantial frequencies of two alleles are maintained in an environment, often because natural selection favors heterozygotes.
Essentially, it's a situation where two different versions of a gene are sustained in a population.
Anaemia Overview:
Reference to 4 forms of anaemia:
Sickle Anemia
Iron Cell Anaemia
Pernicious Anaemia: Deficiency of Vitamin B12
Megaloblastic Anaemia: Due to deficiency of Vitamins B9 (Folic Acid) and B10
Common Issue: Reduced O2 carrying capacity of RBCs in any form of anaemia.
Balanced Polymorphism in Detail:
Underlying Principle: Individuals carrying both alleles (heterozygotes) are often better adapted and have higher survival rates than homozygous individuals who have two copies of the same allele.
Natural Selection Dynamics:
Heterozygotes are preferred by nature.
This preference facilitates balancing selection, leading to equilibrium in the gene pool.
Classical Example: Shape of RBCs in Sickle Cell Trait vs. Normal:
Sickle Cell Trait: Presence of sickle-shaped RBCs can lead to sickle cell anaemia symptoms.
What is Heterozygous Advantage:
Individuals with one sickle cell allele and one normal allele.
Benefits:
No clinical symptoms of sickle anaemia.
Resistance to malarial infection as Plasmodium struggles to invade their RBCs.
Outcome: Heterozygotes are protected from both malaria and severe sickle cell symptoms
2. Transient Polymorphism
Definition:
Transient Polymorphism: A type of polymorphism characterized by a continuous change in the frequency of a character over time, resulting in one form gradually replacing another. This condition is temporary and often a result of directional natural selection.
Characteristics:
Represents a temporary condition/situation.
Typically a byproduct of natural selection in a particular direction (Directional Natural Selection).
After some time, it often reverts back to the original position.
Classical Example: Industrial Melanism in Moths:
Biston bitularia (lighter moth) and Biston carbonaria (darker moth) demonstrated transient polymorphism during the industrialization process in England.
Environmental Impact:
In areas with more pollution, Biston carbonaria had a survival advantage due to its darker coloration.
Conversely, when pollution levels decreased, Biston bitularia gained an advantage.
This selective advantage was not permanent; it was transient or temporary, based on environmental conditions, showcasing directional natural selection.
Hardy-Weinberg Equilibrium and Factors Affecting Gene Frequency
Hardy-Weinberg Law: States that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
Reasons for Change in Gene Frequency or Disturbance in Equilibrium:
Mutation
Isolation
Migration
Selection
Genetic Drift
Note: All the above factors, except inbreeding, are discussed in conjunction with evolution.
Mendelian Populations
Definition:
Mendelian Population: A group of interbreeding, sexually reproducing individuals sharing a common set of genetic information, with inheritance patterns that adhere to Mendel's laws.
Historical Context:
Foundations laid by Gregor Mendel in the 19th century through his work on pea plants, which established the principles of modern genetics.
Key Characteristics:
Interbreeding:
Capability of individuals within the population to breed with one another.
Ensures exchange and reshuffling of genetic material within the group.
Genetic Isolation:
Typically limited gene flow with outside groups, helping maintain genetic distinctiveness.
Shared Gene Pool:
Collective genetic information carried by all members of the population.
Mendelian Inheritance:
Traits are inherited according to Mendel's laws, including:
Law of Segregation: Two alleles for each trait inherited, separating during gamete formation.
Law of Independent Assortment: Alleles for different traits assort independently during gamete formation, assuming genes are on different chromosomes or significantly spaced on the same chromosome.
Hardy-Weinberg Equilibrium:
Genetic stability over generations in the absence of evolutionary forces like mutation, selection, migration, and genetic drift.
Evolutionary Significance:
Provides a framework for studying how genetic variation and evolutionary forces shape populations over time.
Importance in Genetics:
Fundamental units in population genetics.
Aids in understanding the transmission of genetic traits and evolutionary processes.
Key Terms:
Mendelian Population
Interbreeding
Genetic Isolation
Shared Gene Pool
Mendelian Inheritance
Law of Segregation
Law of Independent Assortment
Hardy-Weinberg Equilibrium
Evolution
Hardy-Weinberg Law
Definition:
Hardy-Weinberg Principle/Law/Equilibrium: A fundamental concept in population genetics that describes a theoretical state where a population is not experiencing evolutionary change, thus maintaining genetic equilibrium.
Practicality:
Though a theoretical concept, achieving this state in reality is highly improbable or, if attained, is only momentary.
Conditions for Equilibrium:
The principle stipulates that gene or allele frequencies in a population will remain constant over generations under certain conditions, indicating no evolutionary changes. These conditions include:
No mutations: Absence of new genetic variations.
No natural selection: Equal survival and reproduction rates among all genotypes.
No genetic recombination: Assuming asexual reproduction or random mating without crossover events.
No genetic drift: Large population size to negate random changes in allele frequencies.
No gene migration: No movement of individuals or gametes between populations.
Stability and Evolution:
When these factors are not in play, the population achieves genetic equilibrium, meaning no evolution occurs.
Evolution as Departure: Evolution is considered a departure from the Hardy-Weinberg equilibrium. When any of the equilibrium conditions are violated, evolutionary change is inevitable.
Causes & Changes which bring down Frequency
Mutation
Mutation is the process by which new genetic variants (alleles) are created through changes in the DNA sequence. Mutations can be caused by environmental factors like radiation or chemicals, or occur spontaneously during DNA replication. They are the primary source of genetic variation, essential for evolution as they provide the raw material on which other evolutionary forces can act.
Isolation
Isolation in genetics refers to the separation of populations preventing gene flow, often leading to speciation. There are various forms of isolation, like geographical, reproductive, or behavioral isolation, each contributing to the genetic divergence of populations. Over time, isolation can result in significant genetic differences between populations and possibly the formation of new species.
Geographic Isolation:
Physical Barriers: Natural physical barriers such as mountains, rivers, or oceans can prevent populations from interbreeding.
Distance: Populations separated by vast distances may have limited or no interaction, leading to isolation.
Habitat Differentiation: Different populations might adapt to different habitats within the same geographic area, leading to separation.
Reproductive Isolation:
Temporal Isolation: Populations may breed at different times of the year or day.
Behavioral Isolation: Different mating behaviors or rituals can prevent different populations from interbreeding.
Mechanical Isolation: Physical differences can prevent successful mating between populations.
Gametic Isolation: Even if mating occurs, the sperm and egg cells may be incompatible.
Ecological Isolation:
Populations adapted to different ecological niches or environments within the same area may become isolated from one another.
Social or Behavioral Isolation:
Social Structure: Differences in social structure or behavior may lead to isolation.
Mating Preferences: Preferences for certain traits in mates can lead to isolation.
Genetic Isolation:
Chromosomal Differences: Differences in chromosome number or structure can prevent successful reproduction.
Hybrid Inviability or Sterility: Hybrids may be inviable or sterile, preventing gene flow between populations.
Artificial Isolation:
Human Activity: Human activities like habitat destruction, the creation of artificial barriers, or the introduction of invasive species can lead to isolation.
Migration and Colonization:
Populations that migrate or colonize new areas may become isolated from their parent population.
Catastrophic Events:
Natural Disasters: Events like floods, fires, or volcanic eruptions can create barriers leading to isolation.
Migration
Migration (or gene flow) refers to the movement of individuals (and their genetic material) between populations. It tends to reduce genetic differences between populations and can introduce new genetic variants to a population, potentially affecting its evolutionary trajectory. Migration is a crucial factor in the spread of genetic traits across geographic and population boundaries.
1. Economic Reasons:
Job Opportunities: Individuals or groups may migrate in search of better employment opportunities and improved economic conditions.
Economic Downturn: In regions experiencing economic downturns, people might migrate to areas with more robust economies.
Better Living Standards: The quest for better living conditions, higher wages, or more secure employment can drive migration.
2. Environmental Reasons:
Natural Disasters: Events like floods, hurricanes, earthquakes, or volcanic eruptions can force populations to migrate.
Climate Change: Changes in climate conditions affecting agriculture or natural resources can drive migration.
Resource Scarcity: Scarcity of resources such as water or fertile land can prompt migration.
3. Political and Social Reasons:
Conflict and War: Individuals often flee areas of conflict, war, or civil unrest.
Political Repression: Political repression or human rights abuses can drive migration.
Social Mobility: The desire for social mobility and a better quality of life can motivate migration.
4. Educational Reasons:
Higher Education: Individuals may migrate to access better educational resources or institutions.
Research Opportunities: Researchers might migrate to regions with better facilities, funding, or collaborative opportunities.
5. Health Reasons:
Access to Healthcare: Migration can occur in search of better healthcare facilities or medical treatments.
Health Crises: Epidemics or health crises can prompt migration away from affected areas.
6. Cultural Reasons:
Family Reunification: Individuals might migrate to reunite with family members.
Cultural Exchange: Some may migrate for cultural exchange or to experience different ways of life.
7. Genetic and Evolutionary Reasons (in non-human populations):
Resource Availability: Animal populations might migrate in response to the availability of food, water, or mates.
Habitat Suitability: Changes in habitat suitability due to seasonal variations can drive migration.
8. Legal Reasons:
Asylum Seeking: Individuals may migrate to seek asylum from persecution.
Legal Systems: Some might migrate to regions with more favorable legal systems or regulations.
Selection
Selection is the process by which certain traits become more common in a population due to differential survival and reproduction of individuals. Natural selection operates on the principle of survival of the fittest, where advantageous traits become more common over generations. It's a primary mechanism of evolution and can lead to adaptations to changing environmental conditions, shaping the genetic composition of populations.
Selection, in evolutionary biology, refers to the process by which certain traits become more common in a population due to the differential survival and reproduction of individuals. The underlying mechanisms and reasons for selection can be complex and multifaceted. Here are some key factors or reasons driving selection:
Environmental Adaptation:
Resource Availability: Selection may favor traits that enable better exploitation of available resources like food, water, or shelter.
Climate Adaptation: Traits that confer survival advantages in specific climatic conditions are likely to be selected for.
Predator-Prey Interactions:
Predator Avoidance: Traits that help individuals avoid predation will be favored by selection.
Efficient Predation: In predators, traits that improve hunting success are likely to be selected for.
Reproductive Success:
Mate Attraction: Traits that increase attractiveness to the opposite sex or competitive advantage in mate acquisition are subject to sexual selection.
Fertility and Offspring Survival: Traits that enhance fertility and the survival of offspring will be favored.
Disease Resistance:
Immune Function: Selection tends to favor genetic variants that confer resistance to diseases prevalent in the environment.
Social and Cooperative Interactions:
Group Survival: Traits promoting cooperative behavior might be selected for if they enhance group survival and reproductive success.
Mutation:
Novel Traits: Occasionally, mutations can introduce novel traits that may confer a survival or reproductive advantage, subjecting them to selection.
Human Influence:
Artificial Selection: Humans have selectively bred plants and animals for desired traits, a process known as artificial selection.
Habitat Alteration: Human alteration of habitats can create new selection pressures, favoring traits that confer advantages in altered conditions.
Competition:
Resource Competition: Traits that provide an edge in competing for limited resources are likely to be selected for.
Behavioral Adaptations:
Learning and Innovation: In some species, the ability to learn from experiences and innovate solutions to problems can be favored by selection.
Molecular and Genetic Factors:
Genetic Drift: Sometimes, selection pressures might be influenced by random genetic drift, especially in small populations.
Inbreeding
Definition and Process
Inbreeding: A non-random mating pattern involving closely related individuals leading to offspring that share a significant portion of their gene pool.
Results from the selective breeding or non-random mating where there's a high genetic overlap.
Notable for circulating both desirable and non-desirable traits within a population.
Consequences of Inbreeding
Leads to homozygosity, creating populations that are genetically weaker, less adaptable, and less successful in diverse environments.
Lack of genetic diversity reduces adaptability, making populations vulnerable to new climatic conditions or environmental changes.
Risk of population collapse due to inability to handle climatic or environmental stress.
Absence of new genes from external sources, resulting in no enhancement in genetic diversity.
Many potentially beneficial genes are lost, a process exacerbated by continued inbreeding.
Leads to Inbreeding Depression:
Scenario where the genes cannot cope with new environmental circumstances due to reduced genetic diversity.
Examples of Inbreeding Consequences
Royal Family of Britain:
Numerous descendants with hemophilia traced back to Queen Victoria.
Hemophilia: An X-linked disorder causing increased blood clotting time, also known as "Christmas disease" (related to clotting factor IX deficiency).
Tribal Populations:
Facing extinction due to endogamy (marrying within a specific community).
Hiroshima and Nagasaki Case Studies:
Post-World War II bombings led to extensive mutations in children exposed to intense radiation.
Social stigma and government policies promoted inbreeding and consanguineous marriages.
Resulted in a sharp increase in genetic disorders, mortality rates, and a significant decrease in life expectancy.
Reasons for Inbreeding
Consanguineous Marriages: Marrying cousins or close relatives.
Religious and Cultural Practices: Traditions that encourage marriages within the same community or clan.
Caste Endogamy: Marriages restricted within the same caste.
Geographical Isolation: Particularly in tribes, leading to a limited pool of potential mates.
Small Population Size: Fewer individuals to choose from for mating, increasing the chances of inbreeding.
Anthropological Insights
Studies emphasize the importance of random mating to prevent inbreeding depression.
Encourages the expression of multiple genes and the interplay of dominant and recessive alleles.
Results in a stronger, more adaptable population capable of surviving and thriving in various conditions.
Genetic Drift
Genetic Drift refers to random fluctuations in allele frequencies in a population due to chance events. It's more pronounced in small populations and can lead to the loss or fixation of alleles over time, reducing genetic variation. It plays a critical role in the evolution of isolated populations and can lead to speciation under certain conditions.
Selection, in evolutionary biology, refers to the process by which certain traits become more common in a population due to the differential survival and reproduction of individuals. The underlying mechanisms and reasons for selection can be complex and multifaceted. Here are some key factors or reasons driving selection:
Environmental Adaptation:
Resource Availability: Selection may favor traits that enable better exploitation of available resources like food, water, or shelter.
Climate Adaptation: Traits that confer survival advantages in specific climatic conditions are likely to be selected for.
Predator-Prey Interactions:
Predator Avoidance: Traits that help individuals avoid predation will be favored by selection.
Efficient Predation: In predators, traits that improve hunting success are likely to be selected for.
Reproductive Success:
Mate Attraction: Traits that increase attractiveness to the opposite sex or competitive advantage in mate acquisition are subject to sexual selection.
Fertility and Offspring Survival: Traits that enhance fertility and the survival of offspring will be favored.
Disease Resistance:
Immune Function: Selection tends to favor genetic variants that confer resistance to diseases prevalent in the environment.
Social and Cooperative Interactions:
Group Survival: Traits promoting cooperative behavior might be selected for if they enhance group survival and reproductive success.
Mutation:
Novel Traits: Occasionally, mutations can introduce novel traits that may confer a survival or reproductive advantage, subjecting them to selection.
Human Influence:
Artificial Selection: Humans have selectively bred plants and animals for desired traits, a process known as artificial selection.
Habitat Alteration: Human alteration of habitats can create new selection pressures, favoring traits that confer advantages in altered conditions.
Competition:
Resource Competition: Traits that provide an edge in competing for limited resources are likely to be selected for.
Behavioral Adaptations:
Learning and Innovation: In some species, the ability to learn from experiences and innovate solutions to problems can be favored by selection.
Molecular and Genetic Factors:
Genetic Drift: Sometimes, selection pressures might be influenced by random genetic drift, especially in small populations.
These factors represent a range of environmental, social, and genetic influences that drive the process of selection, shaping the evolutionary trajectories of populations and species over time. Through understanding these mechanisms, scientists can better comprehend the complex dynamics of evolution and adaptation.
Concept of Genetic Load
Overview
Also known as Genetic Burden or Burden Load.
Represents the reduced biological fitness in a given population due to the presence of deleterious genes.
Governs the risk of disease occurrence and related deaths for genetic reasons.
Definition
As per geneticist Crow, genetic load is the reduction in the fitness of the average genotype in a population compared to the most fit genotype.
More evident in populations with prevalent genetic disorders, especially those practicing inbreeding or living in geographical isolation.
Rhesus Protein Factor
Found on Red Blood Cells (RBCs).
Determines whether an individual is Rh-positive (Rh+) or Rh-negative (Rh-).
Mismatched blood transfusion (e.g., group A blood to group B individual) can cause RBC clumping.
Types of Genetic Load
Incompatibility Load
Occurs when certain genotypes cannot survive in an environment due to the presence of specific other genotypes.
Classical example: Rhesus (Rh) incompatibility between an Rh+ fetus and an Rh- mother.
First pregnancy with Rh+ fetus usually results in a healthy child but generates anti-Rh antibodies in the mother.
Subsequent pregnancies with an Rh+ fetus cause maternal anti-Rh antibodies to enter the fetal blood, leading to antigen-antibody reactions and destruction of fetal RBCs, manifesting blood-related disorders in the fetus.
Mutational Load
Result of genetic changes such as deletions, substitutions, or translocations that alter gene expression.
Mutations mask the expression of average traits, as seen in genetic disorders like sickle cell anemia, hemophilia, etc.
Segregational Load
Arises from the breakdown of genetic correlations and linkages.
Mainly caused by two factors: inbreeding and migration.
Inbreeding: Encourages the circulation and potential dominance of deleterious alleles.
Migration: Prevents the introduction of new, potentially beneficial alleles from outside populations.
Leads to the breakup of co-existing beneficial alleles, promoting the inheritance of less advantageous traits.
Key Concept: Genetic Load refers to the cost of maintaining deleterious genes within a population, significantly impacting the population's overall health and fitness. It's particularly pronounced in communities practicing inbreeding or those isolated, leading to an increased prevalence of genetic disorders and decreased adaptability. Different types of genetic loads — incompatibility, mutational, and segregational — elucidate various genetic phenomena adversely affecting populations.
Consanguineous vs. Non-Consanguineous Mating
Consanguineous Mating
Definition: Involves mating between individuals who are closely related, typically having a common ancestor within the last 3 to 5 generations.
Effects and Prevalence:
Violates the Hardy-Weinberg equilibrium, a principle stating that genetic variation remains constant in a population that is not experiencing evolutionary changes.
Common forms include cousin marriages and avunculate (uncle-niece, aunt-nephew) marriages.
Avunculate marriages are less common but observed in regions like South India (Andhra Pradesh, Karnataka).
Maternal cousin marriages are more prevalent than paternal ones.
Globally observed, with notable instances in Southern India and Japan.
Primary Reasons:
Socio-cultural factors drive these marriages, with the belief of greater stability and compatibility between spouses.
A study by Beetal (2001-2008) outlined motivations for consanguineous marriages:
Preservation of property and wealth within the family.
Keeping daughters geographically close post-marriage, allowing for continued familial interactions.
Propagation of desirable characteristics, cultural values, and strengthening of social relations within the community.
Reinforcement of family ties and solidarity.
Other Factors:
Geographical: Isolation leads to endogamy (marrying within a specific community).
Demographic: Small or stigmatized populations, as seen post-World War 2 in Hiroshima and Nagasaki.
Non-Consanguineous Mating
Involves individuals who are not closely related, broadening the genetic diversity within offspring.
Promotes genetic health of the population by reducing the likelihood of inheriting deleterious recessive alleles.
Encouraged by various anthropological studies to avoid issues like inbreeding depression.
Comparative Impacts
Consanguineous mating increases the risk of genetic disorders due to the higher probability of expressing recessive deleterious alleles.
Non-consanguineous mating is generally healthier for the genetic diversity and robustness of a population, enhancing adaptability and resilience against environmental changes.
Key Concept: Consanguineous mating, prevalent due to various cultural, social, and geographical reasons, poses significant genetic risks, leading to increased instances of genetic disorders within families or communities. In contrast, non-consanguineous mating promotes genetic diversity and is advantageous for the overall genetic health of the population.
Genetic Effects of Consanguineous & Cousin Marriages
Consanguinity and Health Challenges
General Perception:
Healthcare professionals and genetics specialists concur that consanguineous marriages elevate the risk of genetic disorders.
Fertility and Mortality:
Research by Beetle and Block indicates a paradox: fertility rates are slightly higher in consanguineous groups, yet so are stillbirths and infant mortality, compared to populations with random mating.
Birth Defects:
Instances of congenital abnormalities are 2-3% more prevalent in consanguineous communities than in non-related populations in the same regions.
Homozygosity and Genetic Disorders:
Consanguinity fosters homozygosity (both alleles are identical, either dominant or recessive), catalyzing the frequent emergence of disorders linked to recessive genes, such as albinism (characterized by an absence of melanin pigment).
Case Study – Post-Nuclear Japan:
In areas affected by nuclear attacks, enforced inbreeding led to escalated rates of congenital deformities and infant mortalities.
Compensatory Fertility Response:
Increased infant mortality rates compel a rise in fertility rates, as communities strive to offset the loss.
Strategies for Mitigation
Preconception Genetic Counseling:
Identified as a crucial measure to prevent or minimize the incidence of inherited genetic anomalies.
Cultural Sensitivity:
The efficacy of genetic counseling programs amplifies when tailored to respect the cultural nuances of the target community.
Role of Anthropological Studies:
Instrumental in understanding and integrating cultural sensitivities, thereby enhancing the success rate of genetic counseling initiatives.
Conclusion
Populations engaged in inbreeding require comprehensive preconception genetic counseling to curb the prevalence of inheritable genetic conditions. The success of such initiatives hinges significantly on their alignment with the cultural context, underlining the indispensable role of anthropological insights.
Key Highlight: Homozygosity, a common consequence of consanguineous unions, can activate the expression of deleterious recessive traits, underscoring the critical need for preemptive genetic counseling and the incorporation of cultural competencies in healthcare strategies.
✅Unit 9.4 : Chromosomes and chromosomal aberrations in man, methodology
Topics of this Unit
1. Numerical & Structural Abberations (Disorders)
2. Sex Chromosomal Abberation
3. Autosomal Abberation
Introduction
Note: Abberation & Mutation is same thing
Classification of Mutation
Intrachromosomal Aberrations:
General: Alterations within a single chromosome.
Types:
Deficiency:
Partial loss of chromosomal material.
Example: Original sequence ATGCGCGCATAT becomes ATGCGCGCAT, indicating a missing segment.
Deletion:
Complete removal of a chromosome segment.
Involves deficiency as a segment is entirely absent.
Note: Terms 'deficiency' and 'deletion' are often used interchangeably.
Inversion:
Segment within a chromosome is reversed end-to-end.
Can lead to issues like sterility or infertility.
Interchromosomal Aberrations:
General: Changes involving more than one chromosome or segments from different chromosomes.
Types:
Duplication:
Production of one or more copies of any piece of DNA, including a gene or even an entire chromosome.
Translocation:
Segment of one chromosome becomes attached to another.
Examples:
Cat Cry Syndrome (Cri-du-chat):
Caused by the deletion of the short arm of the 5th chromosome.
Characterized by a high-pitched cry in infants, resembling a cat's cry.
Chronic Myeloid Leukemia (CML):
Result of a translocation between chromosomes, leading to blood cancer.
Key Concepts: While intrachromosomal aberrations involve changes within a single chromosome (like deficiency, deletion, and inversion), interchromosomal aberrations involve changes between different chromosomes or their parts (like duplication and translocation). These genetic alterations can lead to various health conditions, from specific syndromes to cancers, or reproductive challenges like infertility.
Types of Mutation
Gene Mutation
Introduction
Gene Mutation refers to changes in the expression of a gene.
These alterations occur due to modifications in the nucleotide sequence, number, or type.
Consequently, gene mutation results in changes in gene expression.
Nucleoid is a smaller unit of nucleic acid, whereas Nucleotide is composed of a nucleoside and a phosphate group.
Types of Mutation
Spontaneous Mutation
These mutations arise spontaneously, often due to unknown internal factors, and lead to changes in gene expression.
While these mutations are random and natural, they are generally not harmful.
Frameshift Mutation
Caused by inversions or deletions in base pairs, leading to a shift in the reading frame of gene sequences.
Diagram
Induced Mutation
These mutations occur in response to exposure to specific external factors or triggers.
Such external factors are referred to as Mutagens.
Diagram
Chromosomal Mutation
Summary
Summary of Mutation
Autosomal Abberation - From Pg 56 to 63
Comparative Analysis
Feature/ Syndrome
Down Syndrome (Trisomy 21)
Edward Syndrome (Trisomy 18)
Patau Syndrome (Trisomy 13)
Cat Cry Syndrome (5p- or Cri du Chat)
Chromosome Abnormality
Trisomy 21
Trisomy 18
Trisomy 13
Deletion of the short arm of chromosome 5
Life Expectancy
Many live into adulthood; median life expectancy is around 60 years
Many have:
- Kidney malformations- Breathing and feeding difficulties
Many have:
-Seizures
- Brain abnormalities
- Feeding and swallowing difficulties
- Speech delays
- Motor delays
Down Syndrome
Edwards Syndrome
Patau Syndrome
Cat Cry / Cri Du Chat Syndrome
Sex Chromosomal Mutation - From Pg 56 to 63
Comparative Analysis
Feature/Syndrome
Klinefelter Syndrome (47,XXY)
Turner Syndrome (45,X)
XYY Syndrome (47,XYY)
Triple X Syndrome (47,XXX)
Intersex
Syndrome
Chromosome Abnormality
At least one extra X chromosome in males (most commonly one, i.e., XXY)
Complete or partial absence of one X chromosome in females
An extra Y chromosome in super males
An extra X chromosome in super females
A range of different chromosomal configurations outside the typical XX or XY
Physical Features
- Taller than average stature
- Small testes
- Reduced facial and body hair
- Short stature
- Webbed neck
- Low-set ears
- Broad chest with widely spaced nipples
- Taller than average stature
- Most physical features are similar to males with XY chromosomes; few distinctive physical signs
- Taller than average stature
- Most physical features are similar to females with XX chromosomes; few distinctive physical signs
Highly variable, can include ambiguous genitalia, inconsistency between external genitalia and internal reproductive organs, or typical male or female genitalia with atypical reproductive function
Fertility
Often infertile due to lower levels of testosterone and reduced sperm production
Usually infertile; ovarian insufficiency is common
Most are fertile, but there may be an increased risk of producing sperm with an abnormal number of chromosomes
Most are fertile, with normal sexual development
Varies widely depending on the specific intersex condition; can range from fertile to infertile
Cognitive/Developmental Features
- Possible learning disabilities
- Delayed speech and language development
- Normal intelligence, though some may have learning disabilitie
- Possible social interaction difficulties
- Intelligence within the normal range, though some may have learning disabilities
- Increased likelihood of ADHD or autism spectrum disorders
- Intelligence within the normal range, though some may have learning disabilities
- Increased likelihood of speech and language difficulties
Varies widely; there is no specific cognitive or developmental profile associated with being intersex
Other Health Concerns
- Risk of gynecomastia (developing breast tissue)
- Risk of autoimmune disorders, osteoporosis, breast cancer, and other health issues
- Generally healthy, but some studies suggest a higher incidence of behavioral and developmental issues
- Generally healthy, though there may be a slightly increased risk of developmental delays and behavioral and emotional difficulties
Depends on the specific intersex condition; can include hormone imbalance, susceptibility to certain cancers, and other health issues
Klinefelters Syndrome
Turners Syndrome
Super Males and Super Females
Intersex Syndrome
4. Genetic Imprint in Human Disease
Definition
Gene imprinting or genomic imprinting refers to the phenomenon where only one copy of a gene is active while the other remains inactive. This contrasts with the typical genetic function where both copies of a gene (one inherited from each parent) are usually active in an individual's cells.
Process
Inheritance:
Normally, individuals inherit two gene copies: one from the father and one from the mother, with both typically being active in the cells.
Selective Activation:
In certain cases, only one of these two copies is "turned on" or expressed. This can depend on the parent of origin, a process that's not random but rather determined by the gene's parental source. Otherwise, it's due to random selective activation, wherein either copy could be expressed without parental bias
Methylation
The mechanism through which genes are deactivated, or silenced, is primarily through DNA methylation. Specifically, the repressed alleles are methylated, rendering them inactive, while the active ones are unmethylated and thus functional
Prevalence and Mystery
Only a small percentage of all human genes undergo imprinting. The criteria or mechanisms that dictate why certain genes are subject to imprinting while others are not have yet to be fully understood or deciphered.
5. Genetic Screening & Genetic Counseling
Overview
Purpose: Medical, psychological, and social counseling.
Key Concept: Communication of genetic information in an accessible, meaningful manner to patients, parents, and families.
Genetic Counseling
Definition: Process providing individuals or families with information, support, advice, and guidance from health professionals and counselors.
Objective: Enhance ability to cope with diagnosis, screening, and management of genetic disorders.
Scope:
In its broader form, includes understanding and adapting to implications of genetic contributions to disease.
Conventionally involves collecting family and medical history, risk assessment, genetic testing, informed consent, psychosocial assessment, and support.
Educational Aspect:
Aims to inform and advise clients, students, and at-risk relatives about the nature of the disorder, odds of development, and risk of transmission to future generations.
Highlighted by WHO: All pregnant women should be offered genetic counseling, testing, and screening.
Target Groups:
Families with a history of genetic disorders.
Populations practicing inbreeding.
Groups exposed to chemicals or radiations.
Primary Goal: Improve odds of birthing a healthy baby through preemptive action.
Genetic Screening
Definition: Medical tests identifying changes in chromosomes, genes, or proteins.
Purpose: Confirm/rule out suspected genetic conditions or assist individuals in understanding their chances of developing or passing on a genetic disorder.
Types of Tests:
Biochemical genetic tests, chromosomal mapping, or gene tests conducted at various life stages.
Newborn screening: Conducted immediately after birth to detect genetic disorders.
Diagnostic testing: Performed pre- or post-birth to check for specific genetic/chromosomal conditions.
Carrier testing: Offered to individuals with a family history of genetic disorders to identify carriers of a single gene mutation.
Prenatal testing: Conducted before birth to detect fetal genetic disorders.
Pre-implantation testing: Conducted particularly with ART (Assistive Reproductive Techniques) like IVF, before the zygote attaches to the uterine wall.
Challenges and Considerations
Despite its benefits, genetic screening and testing pose challenges:
Social stigma: Associated with identified genetic conditions.
Privacy concerns: Related to revealing genetic information.
Potential misuse: Of genetic information and testing technologies.
Conclusion: Navigating these challenges requires careful consideration and a balanced approach, emphasizing ethical standards and individuals' well-being
6. Human DNA Profiling (DNA Profiling / DNA Figure Printing)
Concepts and Founders
DNA Profiling, also known as DNA Fingerprinting.
Dr. Alee Jaffrey, regarded as the father of DNA fingerprinting.
Dr. Lalji Singh, recognized as the father of DNA fingerprinting in India.
Fundamental Bases
Rooted in VNTR (Variable Number of Tandem Repeats) and DNA Polymorphism.
Involves determining the nucleotide sequence in specific DNA areas unique to each individual.
Each person possesses a distinct DNA fingerprint; the same degree of polymorphism is present across all bodily specimens of that individual.
This unique sequence acts as an identity marker, applicable for various uses.
Biological Samples for DNA Profiling
Can be conducted on various samples, including:
Blood
Saliva
Hair
Bone
Semen
Nails
Skin
Non-Coding Sequences and Satellite DNA
Human DNA contains non-coding sequences, part of repetitive DNA, typically found at the end of chromosomes, known as Satellite DNA.
The base repetitions occur in tandem with coding sequences; these tandem repeats vary uniquely among individuals.
VNTRs and DNA Polymorphism
VNTRs (Variable Number of Tandem Repeats) form the basis of DNA fingerprinting.
Satellite DNA exhibits polymorphism due to accumulated mutations over time, particularly in non-coding sequences.
VNTRs and DNA polymorphism are crucial for genetic mapping of the human genome.
Applications of DNA Fingerprinting
Paternity and Maternity Disputes: Resolving conflicts by identifying biological parents.
Crime Investigations: Essential in murder and rape cases.
Child Trafficking Victims: Aids in the identification and protection of exploited children.
Sociological and Anthropological Studies: Useful in research on races, ethnicities, and the origin or dispersal of populations.
Disaster Victim Identification: Critical in identifying victims of disasters, road accidents, burn events, and more.
7. Gene Mapping
Definition and Importance
Gene mapping is the method used to determine the location of genes on a chromosome.
Essential for studying and understanding genetic diseases and abnormalities, including chromosomal aberrations and specific syndromes.
By pinpointing the exact positions of genes, it provides deeper insight into the genetic underpinnings of various diseases.
Applications and Implications
Fundamental in the development of effective treatments or management strategies for genetic diseases.
Facilitates researchers in tracing the inheritance patterns of diseases.
Enables the prediction and prevention of potential genetic disorders in individuals or families predisposed to certain genetic conditions.
Role in Medical Advancements
Contributes significantly to advancements in personalized medicine, allowing for treatments tailored to individuals' genetic makeup.
Plays a crucial role in pharmacogenomics, helping predict individual responses to drugs based on genetic factors.
8. Genome Study
Human Genome Project (HGP)
HGP-Read (1990-2003)
Aimed at sequencing and mapping all the genes - collectively known as the genome - of members of our species, Homo sapiens.
Interdisciplinary Approach:
Required the convergence of expertise in various fields such as mathematics, statistics, biological sciences, and software development.
Led to the emergence of Bioinformatics.
Findings and Features:
The human genome contains approximately 3 billion base pairs.
Major portions of the sequences are non-functional or "junk" DNA.
These noncoding sequences may provide backup for coding sequences.
Less than 2% of the genome is involved in coding for protein synthesis.
There are 25,000 to 45,000 genes in the human genome, with 22,000 to 25,000 being functional; the roles of the rest are yet unknown.
99.9% similarity exists in nucleotide base pairs among all humans.
Genome size or the number of genes is not indicative of an organism's complexity (e.g., a lily flower has 18 times more DNA than humans).
Repetitive DNA is associated with satellite DNA, which can be used for forensic applications and DNA fingerprinting due to their variability among individuals.
India's Involvement:
India did not initially participate in HGP-Read.
Later projects involving genome study included Indian contributions.
HGP-Write (2015-16)
Objective: To synthesize human genomes in a lab ("in vitro").
Potential for new solutions to region-specific diseases through the testing or screening of drugs using synthetic human genomes.
ENCODE (Encyclopedia of DNA Elements):
Aims to determine the roles of non-coding DNA sequences.
Recent studies suggest that even "junk" DNA plays a crucial role in regulating and expressing coding DNA.
Genome India Project & IndiGen (CSIR)
Undertaken by the Department of Biotechnology and CSIR.
Focus on genome studies pertinent to the Indian population.
Applications of HGP
Enhanced understanding of various disorders (cardiovascular diseases, Alzheimer's, cancer) that result from complex gene interactions.
Enables a deeper understanding of the host-pathogen relationship post-genome sequencing.
Facilitates detailed studies of genetic mutations and their consequent changes.
Aids in discerning the regulation of traits by genes and proteins; potentially suppresses genetic disorders in families.
Assists in comparative genomic studies of animals, elucidating disease transmission from animals to humans.
Supports targeted genome sequencing projects like those of cattle genomes, aiding initiatives such as the Biotech Kisan by the Department of Biotechnology, Ministry of Science and Technology.
✅Unit 9.6 : Age Sex & Population Variation as Genetic Markers
ABO Blood Groups
The blood group system in humans was identified through the study of antigens on the surface of Red Blood Cells (RBCs).
Each blood group has specific antigens and antibodies.
Antigens are proteins on the surface of RBCs and are not pathogens.
Antibodies form a response against non-compatible antigens.
The appearance of RBCs varies among individuals based on their blood group due to the presence of different antigens.
Human Blood Group System / ABO Blood Group System
The system is determined by the presence or absence of two surface antigens - antigen a and antigen b.
Additionally, human plasma contains two naturally formed antibodies - anti-a and anti-b.
Compatibility for blood transfusion is established through these antigen and antibody interactions.
Statistical Distribution of Blood Groups in India:
O blood group: 37%
AB blood group: 8-9%
B blood group: 32%
A blood group: 23%
Key Terms:
Antigen: A protein present on the surface of RBCs, responsible for blood group characteristics. Not a pathogen.
Antibody: A blood protein produced in response to and counteracting a specific antigen.
Compatibility: The ability of one blood group to be safely transfused into an individual with another blood group, determined by reactions between antigens and antibodies.
RBCs (Red Blood Cells): Cells in the blood responsible for carrying oxygen, whose surfaces contain specific antigens determining blood groups.
Rh Blood Groups
Rh Factor
The Rhesus factor, first discovered in the Rhesus monkey, is a protein found on the surface of RBCs.
Individuals with this protein are deemed Rh-positive (Rh+).
Those lacking this protein are known as Rh-negative (Rh-).
Rh+ is dominant over Rh-.
Universal donor: O-
Universal accepter: AB+
The Rh factor provides enhanced understanding for blood transfusions.
Incompatible transfusions can trigger antigen-antibody reactions, causing the clumping of RBCs, known as Agglutination.
Rh Incompatibility and Erythroblastosis Foetalis
Occurs when an Rh- mother carries an Rh+ fetus.
The first delivery may not present issues, but subsequent pregnancies can lead to a severe form of anemia in the fetus, known as Erythroblastosis foetalis, due to Rh incompatibility.
Key Concepts
Rh Factor: A protein on RBCs first identified in Rhesus monkeys, determining Rh blood group status (+/-).
Agglutination: The clumping of RBCs caused by an antigen-antibody reaction, typically due to blood transfusion incompatibility.
Erythroblastosis Foetalis: A condition causing severe anemia in an Rh-incompatible foetus, often during subsequent pregnancies of an Rh- mother with an Rh+ foetus.
Universal Donor: Blood type O-, which can be safely transfused to individuals of any other blood group.
Universal Acceptor: Blood type AB+, which can receive blood from any group.
Genetic Markers: Core Concepts
Definition: Genetic markers are specific sequences within the DNA that can be used to identify particular genes, their inherited diseases, or other traits.
They are essentially the genetic identity that segregates independently.
Markers provide a position, location, or hint about the presence or absence of a specific genetic trait.
Function: They help in linking an inherited disease or characteristic with the responsible gene.
Useful in tracking inheritance of nearby genes that haven't been identified yet.
Their known physical locations on chromosomes allow for the tracking of genetic inheritance.
Utility: Genetic markers are crucial for classifying populations by their presence, absence, or the differences in frequency of occurrence.
Inheritance: DNA characters close to each other tend to be inherited together, aiding in the identification process.
Application of Blood Groups as Genetic Markers
Applications of Blood Groups
1.1. Disputed Parenthood: Utilized in resolving cases of uncertain biological relationships, especially in identifying a child's biological mother or father
1.2. Medicolegal Cases: Blood group testing aids in the resolution of various legal matters requiring genetic proof
1.3. Forensic Science: Critical in tracking criminals by enabling the matching of blood types found at crime scenes to suspects
1.4. Blood Transfusion Chemistry: Enhances comprehension of the compatibility of blood types, preventing transfusion reactions
1.5. Organ Transplants: Provides a scientific framework for organ compatibility and rejection prevention
1.6. Blood-Related Disorders: Facilitates improved diagnosis, treatment, and understanding of disorders linked to blood type.
Case Study
2.1. Overview: Alice Brues' research demonstrated that the global distribution of blood groups is influenced by both genetic and environmental factors.
- Methodology: Data was aggregated from over 200 population groups worldwide
2.2. Findings
2.2.1. Lapps/Tundra Populations: Predominantly group A, with a significant majority within this demographic
2.2.2. Asian and Mongoloids: Over 35% exhibit the B blood group, indicative of a substantial prevalence in these populations
2.2.3. American Indians: Group O is most common, occurring in more than 30% of the population
2.3. Conclusion:
- Blood groups serve as vital genetic markers, offering insights into various genetic principles observed in diverse populations
- Key principles include co-dominance, polymorphism, and multiple allelism
- Their application is fundamental to the field of biological anthropology.
Important Concepts
Co-dominance: A form of dominance wherein the alleles of a gene pair in a heterozygote are fully expressed. This results in offspring with a phenotype that is neither dominant nor recessive.
Polymorphism: The occurrence of several different forms or types of individuals among the members of a single species. It is a tool for understanding variability within a population.
Multiple Allelism: The existence of more than two alleles at a single genetic locus in a population. Each individual member of the population can have only two of the possible alleles, but more than two exist in the population's gene pool.
Biological Anthropology: A scientific discipline concerned with the biological and behavioral aspects of human beings, their related non-human primates, and their extinct hominin ancestors
Final Conclusion
Blood groups as genetic markers are instrumental in enhancing our understanding of complex genetic principles and variability among different populations. Their extensive applications range from forensic science to health sciences and anthropological studies, underscoring their significance in diverse research and practical domains.
Genetic Markers in Blood
Rhesus (Rh) factor: A specific protein found on the surface of red blood cells
Rh Factor
The Rhesus factor, first discovered in the Rhesus monkey, is a protein found on the surface of RBCs.
Individuals with this protein are deemed Rh-positive (Rh+).
Those lacking this protein are known as Rh-negative (Rh-).
Rh+ is dominant over Rh-.
Universal donor: O-
Universal accepter: AB+
The Rh factor provides enhanced understanding for blood transfusions.
Incompatible transfusions can trigger antigen-antibody reactions, causing the clumping of RBCs, known as Agglutination.
Rh Incompatibility and Erythroblastosis Foetalis
Occurs when an Rh- mother carries an Rh+ fetus.
The first delivery may not present issues, but subsequent pregnancies can lead to a severe form of anemia in the fetus, known as Erythroblastosis foetalis, due to Rh incompatibility.
Key Concepts
Rh Factor: A protein on RBCs first identified in Rhesus monkeys, determining Rh blood group status (+/-).
Agglutination: The clumping of RBCs caused by an antigen-antibody reaction, typically due to blood transfusion incompatibility.
Erythroblastosis Foetalis: A condition causing severe anemia in an Rh-incompatible foetus, often during subsequent pregnancies of an Rh- mother with an Rh+ foetus.
Universal Donor: Blood type O-, which can be safely transfused to individuals of any other blood group.
Universal Acceptor: Blood type AB+, which can receive blood from any group.
Human Leukocyte Antigen (HLA): Proteins that regulate immune responses
Overview
HLA refers to a set of genes responsible for the major Histocompatibility complex on the short arm of chromosome 6.
They are crucial for the coding of proteins that play a pivotal role in the immune response.
Significant in immune defense and critical in transplant rejections due to their role in self and non-self-recognition.
Function in Immune Response
Central to the body's defense mechanism through self and non-self-identification.
Differentiates between the body's own substances and foreign materials.
If an unfamiliar organ is introduced, it’s recognized as non-self, potentially triggering a rejection.
Role in Transplantation
HLA mismatching: Primary cause of transplant rejections.
The more unrelated the donor, the greater the differences in the HLA complex on chromosome 6, increasing rejection risks.
Preference for closely related individuals for organ or stem cell transplants.
Similarity in the genetic locus results in lesser discrepancies in HLA, reducing the likelihood of rejection.
Graft/Organ Rejection Prevention: Possible through temporary immune suppression.
Typically involves the administration of steroids or other immunosuppressive agents.
Importance in Medical Science
The discovery of HLA bolstered advancements in the field of organ transplantation.
Act as a critical genetic marker in research and development.
The understanding of HLA is fundamental for improving transplant compatibility and success rates.
Histocompatibility
HLA's role in Histocompatibility is paramount.
Transplant rejection primarily occurs due to histocompatibility issues instigated by HLA differences.
Key Concept
Human Leucocyte Antigen (HLA): A gene complex influencing immune response and transplant compatibility, fundamental for self/non-self-recognition, and central to advances in organ transplantation fields.
Haemoglobin (Hb): The oxygen-carrying protein in red blood cells
Hemoglobin
Defined as the oxygen-carrying protein prevalent in red blood cells (RBCs).
Haemoglobin: An essential protein in red blood cells responsible for oxygen transport, pivotal to the overall composition and functional efficacy of blood, working in unison with other cellular components and plasma proteins.
Blood Composition and Function
Overview
Recognized as a crucial connective tissue, blood is indispensable for transporting various substances like gases, waste products, energy sources, and minerals throughout the body.
Proteins in Plasma
Albumins: Primarily responsible for maintaining the osmotic balance within the blood.
Globulins: Act significantly in the immune system, providing defense mechanisms.
Fibrinogen: A key protein that is fundamental for the blood clotting process.
Serums: Refer to plasma from which the clotting factors have been removed.
Blood Cells Table
Parameter
Red Blood Cells (RBCs)
White Blood Cells (WBCs)
Platelets (Thrombocytes)
Count
Approximately 1.5 to 6 million/mm³
Approximately 4000-11000/mm³
Approximately 150,000 to 450,000/mm³
Function
Transport gases due to hemoglobin presence.
Provide immunity by combating infections.
Essential for blood clotting processes.
Characteristics
Red, biconcave, nucleus absent.
Varied shapes, larger, nucleus present.
Small, colorless, without a nucleus.
Types
Not applicable
Lymphocytes, Monocytes, Neutrophils, etc.
Not applicable
Blood Cells Detailed
Red Blood Cells (RBCs)
Count: Roughly 1.5 to 6 million/mm³.
Function: Facilitates gas transport, especially oxygen and carbon dioxide, due to the presence of hemoglobin.
Characteristics: Distinct red color, biconcave shape, and absence of a nucleus.
White Blood Cells (WBCs)
Count: Typically ranges between 4000 and 11000/mm³.
Function: Function as defense cells, integral to the body's immune system.
Types: Diversity includes lymphocytes, monocytes, neutrophils, eosinophils, basophils, with subtypes like B cells and T cells under lymphocytes.
Platelets (Thrombocytes)
Count: Generally around 150,000 to 450,000/mm³ (please note there seems to be a typographical error in the original text, "1L to 4.5L/mm³" is not a standard measurement for platelet count).
Function: They are critical to the blood clotting process, preventing excessive bleeding.
Composition of Blood Visual Representation
Blood Enzymes (BE): Proteins that facilitate chemical reactions in the blood
Overview
Definition: Blood enzymes are proteins instrumental in catalyzing chemical reactions within the blood.
Significance: These enzymes are crucial for various physiological processes and their polymorphism indicates significant genetic variations.
Blood Enzyme Polymorphism
Concept: Variation in blood enzymes exists, leading to differences observed from one individual to another.
Specific Enzymes: Focus particularly on three different blood enzymes:
G6PD (Glucose-6-Phosphate Dehydrogenase):
Function: Plays a critical role in protecting red blood cells from oxidative damage.
Variability: G6PD deficiency varies among populations and individuals, acting as a notable blood marker.
Pyruvate Kinase:
Role: Involved in the division of proteins and the functioning of plasma proteins.
Adenylate Kinase:
Role: Similar to Pyruvate Kinase, it aids in the division of proteins and plasma protein functions.
Geographical and Demographical Variations
G6PD Deficiency Prevalence: More common in regions such as Africa, Southeast Asia, India, and the Mediterranean.
Specific Case - India:
Gender Disparity: G6PD deficiency is observed more frequently in males.
Ethnic Variability: Certain tribal groups exhibit significant levels of G6PD deficiency, including:
Munda
Parajas (specifically in Odisha)
Kharias (located in the Raj Mahal hill region of Jharkhand)
Santhals
Kurukhs
Inference: This deficiency in blood enzymes, particularly G6PD, underscores variations based on regional, racial, or ethnic differences.
Health Task Force Involvement:
Initiative: Formed by the Ministry of Tribal Affairs to address health concerns related to blood enzyme deficiencies among tribal populations.
Observation: The task force noted a considerable prevalence of G6PD deficiency within these groups.
Conclusion:
Blood enzymes, especially those exhibiting polymorphism like G6PD, highlight the significant genetic variations in populations. These variations are often based on regional, racial, or ethnic distinctions, thus serving as important blood markers
Haptoglobins (HP): Proteins that bind free haemoglobin
Haptoglobins (HP)
Definition: Proteins that bind free haemoglobin (HB).
Characteristics & Functions:
Complex of two globulins found in serum.
Transfers free HB to the liver for breakdown:
Contributes to iron release, especially important during iron deficiency.
Role in combating anaemia:
Essential for healthy digestion.
Assists in bile pigment formation:
Bile: A liver secretion containing bilirubin and biliverdin pigments.
Crucial for digestion and emulsification of fats.
Emulsification of fats:
Facilitates the mixing of molecules that do not typically combine.
Produced primarily by liver cells, but also by cells in the skin, lungs, and kidneys.
Health Implications
Deficiency can lead to kidney disorders.
Low levels prevalent in certain populations:
Near zero in U.S. blacks or Brazil's black population, increasing chances of kidney issues.
Tropical parts of Africa have a high prevalence (60-70%).
India and other parts of South Asia typically have low levels.
Populations with very low or absent HP levels are at risk for:
Kidney-related disorders.
Various forms of anaemia.
Transferrins (TF): Proteins that bind and transport iron
Definition: Proteins that bind and transport iron.
Also Known As: TF gene, transferins, siderophilin.
Characteristics & Functions:
Associated with developing RBCs' surfaces and globulins.
Iron-binding beta globulins of blood plasma, also present on developing RBCs:
Assist in extracting iron following the bursting of RBCs.
Main function: Distributes iron post-RBC death.
Directs iron to bone marrow for new RBC production or to the liver for storage.
Formed in the liver.
Critical in iron homeostasis:
Low iron or blood can disturb gaseous exchange and precipitate anaemic conditions.
In response, the liver produces more transferrin.
Humans have 14 different types of transferrins:
Five main types: TF A, TF B, TF C, TF D.
Health Implications:
Significant marker of anaemia:
Essential role in iron distribution and prevention of anaemia.
Immunoglobulins (Gm): Antibodies that play a critical role in immunity
Immunoglobulins (Ig):
Definition: Defence proteins primarily released by lymphocytes.
Types: IgA, IgD, IgE, IgG, IgM.
GM Factor:
Specific to IgG.
Exhibits high variability across different populations.
Importance: Serves as an important genetic marker for distinguishing between races due to its variability.
Structure of Antibody / Immune Globulin (Ig):
Composition:
Four chains: Comprises 2 identical light chains and 2 identical heavy chains.
Chains are interconnected by bonds.
Heavy Chain Features:
Constant regions: Lack variation within the population.
Variable zone: Also known as the antigen-binding zone.
Function: Binds to specific antigens.
Genetic Marker Associations:
Predominantly linked with IgG.
GM factors' variability is useful for:
Race differentiation: Different populations exhibit distinct characteristics related to the GM factor.
Immune response in neonates: Variations in light chains of Ig contribute to triggering immune responses in newborns.
Population Specificity of GM Factors:
High predominance observed in:
Si Dama (Sidama) tribe of Ethiopia.
Ainu tribe of Japan.
Physiological Characteristic (In Different Cultural & Socio Economic Groups)
Haemoglobin Level
Important Facts about Haemoglobin (HB)
Global Average Levels
Males: Average HB globally is 14 to 16 grams/deciliter.
Females: Average HB globally is 12 to 15 grams/deciliter.
Average Levels in India
Males: 13 to 15 grams/deciliter.
Females: 10 to 13 grams/deciliter.
Consequences of Deficiency
Low HB leads to anaemia, resulting in a reduced oxygen supply throughout the body.
Case Study: Chattopadhyay's Research on Oraons or Coorg
Findings
Over 50% of adult females and boys were found to be anaemic.
Almost 0% of men were anaemic.
Implications
These results indicate a presence of strong patriarchy and dietary differences within the community.
Haemoglobin Variations
Geographical Influence
HB is typically higher in individuals living at higher altitudes due to the lower oxygen concentration, necessitating an increase in RBCs for adequate oxygen transport.
Genetic Disorders Affecting HB
Thalassemia: A condition where the beta chains of haemoglobin are impaired, disrupting the normal function of HB and gas transport.
Sickle Cell Anaemia: Another genetic disorder affecting HB.
Noteworthy Point
Variations in HB can also occur due to other blood-related disorders like the ones mentioned above.
Body Fats / Adipose Tissue
Overview and Function
Adipose tissue, a type of connective tissue, plays a crucial role in:
Energy storage: Stores energy in the form of lipids.
Insulation: Acts as a "kushan," insulating the body externally and safeguarding internal organs.
Thermal adaptation: Vital in both warm and cold adaptation, found throughout the skin across the body.
Geographical and Environmental Influences
Temperature Adaptation:
Hotter Areas: Less adipose tissue.
Colder Climates: More adipose tissue, especially observed in Eskimos, Lapps, and high-altitude dwellers facing low-temperature extremes, necessitating extra fat deposits for warmth.
Population-specific Observations:
Bushman of Kalahari: Notable for significant fatty deposits in thighs and buttock region, particularly in less migratory populations. This pattern differs from other nearby groups with higher migration tendencies.
Andra Pradesh Tribes: A study by Nirmala et al. found high blood pressure in a majority of the population, linked to excessive deposition of intra-abdominal fatty tissues, influenced by dietary patterns.
Health Implications
Essential for healthy living through roles in energy provision in extraordinary conditions and overall body thermal regulation.
Risks:
Excessive fatty deposits around the belly, internal organs, and blood vessels can lead to obesity, blood pressure complications, and severe threats like cardiac arrest.
Dietary Management:
Polyunsaturated fatty acids recommended by physicians for heart and blood pressure patients, regulating bad cholesterol levels and preventing dehydrogenation.
Essential fatty acids not produced in the human body; must be obtained through diet:
Linolic acid, linolenic acid, arachidonic acid.
Examples include omega-3 and omega-6, known not to deposit over the arteries.
Safola oil is highlighted as a heart-healthy option.
Life Style Disorder (2022)
Overview of Lifestyle Disorders
Disorders primarily attributed to personal behaviors and environmental factors leading to health problems.
Role of Fats in Health
Trans Fats and Saturated Fatty Acids:
These are types of unsaturated fats that behave like saturated fats due to their altered chemical structure.
Lead to a rise in "bad" cholesterol (LDL - Low-Density Lipoproteins), causing disruptions in body functioning and increasing the prevalence of unhealthy individuals within a population.
These unhealthy fatty acids accumulate in various body tissues, causing health variations among populations and thus acting as a marker.
Fatty Acid Synthesis
In Plants:
Can synthesize all required fatty acids for their physiological processes.
In Humans and Animals:
Can synthesize most required fatty acids, but not all.
Essential Fatty Acids: Linolic acid, linolenic acid, and arachidonic acid must be present in the diet; hence, they're termed as "essential." These are provided through diet as PUFAs (Polyunsaturated Fatty Acids), predominantly found in edible oils of both plant and animal origin.
Cholesterol Types and Implications
Good Cholesterol: HDL - High-Density Lipoproteins.
Bad Cholesterol: LDL - Low-Density Lipoproteins.
An increase in arterial pressure can result in heightened blood flow, forcing the heart to pump blood faster, potentially leading to a sudden heart attack.
Adverse Effects of Trans Fats
Due to their modified chemical structure, trans fats raise levels of bad cholesterol (LDL) and decrease good cholesterol (HDL), contributing to lifestyle disorders like heart diseases.
Graphical Representation
The provided diagram (not visible here) likely illustrates the structural differences between trans fats and other fatty acids, or the mechanisms by which trans fats impact cholesterol levels and health
Pulse Rate
Definition: The number of heartbeats per minute; can be tracked at multiple body locations including the neck, wrist, elbow, and top of the foot.
Healthy Range:
Adults: Typically 60 to 100 beats per minute (bpm).
Optimal: 60 to 80 bpm.
Bradycardia: Less than 60 bpm, potentially leading to heart block if persistent.
Tachycardia: More than 100 bpm, potentially resulting in increased blood pressure.
Newborns: 100-140 bpm.
Ideal: 100-120 bpm.
Blood Pressure (BP)
Definition: The pressure exerted by the blood upon the walls of blood vessels.
Systolic: Upper limit (heart's contraction).
Healthy range: 100-130 millimeters of mercury (mm Hg).
Ideal: 120 mm Hg.
Diastolic: Lower limit (heart's relaxation).
Healthy range: 60-90 mm Hg.
Ideal: 80 mm Hg.
Variations:
Hypertension: High BP.
Hypotension: Low BP.
Age Variations in BP:
Infants: 70 to 90 mm Hg.
Children: 90 to 110 mm Hg.
Puberty: 110 to 120 mm Hg.
Adults: 100 to 130 mm Hg.
Old Age: 130 to 150 mm Hg.
Noteworthy: BP tends to increase with age due to the lack of healthy cells to replace dead ones.
Key Terms
Bradycardia: A slower than normal heart rate.
Tachycardia: A faster than normal heart rate.
Hypertension: Elevated blood pressure.
Hypotension: Lowered blood pressure.
Systolic Pressure: The upper BP number, indicating pressure during the heart's contraction.
Diastolic Pressure: The lower BP number, indicating pressure during the heart's relaxation.
Respiratory Functions
Respiratory Functions
Breathing Process:
Net intake of O2: Oxygen is primarily taken in during inhalation.
Net removal of CO2: Carbon dioxide is expelled from the body during exhalation.
Oxyhemoglobin: Hemoglobin loaded with oxygen; crucial for transporting O2 to various body parts.
Carbaminohemoglobin: Hemoglobin carrying carbon dioxide; vital for picking up CO2 from different body tissues.
Breathing Rate:
Healthy Range in Adults: Typically, the respiratory rate is 12 to 16 breaths per minute, with the optimal rate being approximately 14.
Variations: Influenced by factors such as age, overall health, allergic reactions, and geographic location's topography.
Vital Signs and Environmental Indicators:
Pulse Rate: Along with blood pressure and respiratory activity, reflects the body's current state.
Blood Pressure (BP): Helps in assessing the circulatory system's status.
Respiratory Activity: Indicates the efficiency and health of the respiratory system.
Population Studies: These parameters are crucial for understanding the environments populations inhabit, differences in health status, gender-based disparities, and age-related variations.
Important Concepts
Oxyhemoglobin: Responsible for the transportation of oxygen from the lungs to the body's tissues.
Carbaminohemoglobin: Facilitates the return transport of carbon dioxide from the tissues to the lungs.
Healthy Breathing Rate: The standard respiratory rate in a relaxed adult, indicative of proper lung function and efficiency.
Vital Signs: Pulse, blood pressure, and respiratory rates are key indicators of health and physiological function, reflecting the body's responses to various internal and external factors.
Diagram
[Respiratory Process]
Inhalation: O2 enters -> Lungs -> Blood -> Oxyhemoglobin forms
Transportation: Oxyhemoglobin -> Body tissues -> O2 released
Cellular Utilization: O2 -> Used in cellular processes -> CO2 produced
Return Transportation: CO2 -> Blood -> Carbaminohemoglobin forms
Exhalation: Carbaminohemoglobin -> Lungs -> CO2 expelled
Sensory Perceptions
Types of Receptors and Associated Perceptions
Variability exists in different populations.
Five primary types:
a. Mechanoreceptors (Touch)
b. Auditory receptors (Sound)
c. Photoreceptors (Vision)
d. Gustatory receptors (Taste)
e. Olfactory receptors (Smell)
Specifics of Receptor Types
Mechanoreceptors: Respond to mechanical pressure or distortion.
Auditory receptors: Detect sound waves.
Photoreceptors: Respond to light wavelengths.
Gustatory receptors: Detect tastes.
Olfactory receptors: Sense odors.
Prominently Surveyed Receptors
Gustatory receptors receive special attention.
Ability to taste PTC (phenylthiocarbamide) varies among populations.
Photoreceptor Studies
Commonly through the lens of red-green color blindness.
Receptor Stimulation and Signal Conversion
Receptors convert external stimuli into nerve impulses.
Impulses transmitted to the brain for interpretation.
Variability Among Populations
Some variability in receptor types across different races and cultures.
Most receptors occur within an average range across populations.
Exceptions may be due to pathogenic conditions or socio-cultural factors
