Neo-Darwinism is a modified version of Darwin's theory of evolution by natural selection. It incorporates genetic variation as the raw material for evolution. Genetic variation arises from sources like mutations, recombination, and chromosomal changes. Natural selection leads to differential reproduction of adaptive variants, increasing their frequency over generations. Reproductive isolation maintains distinctiveness between species. According to Neo-Darwinism, evolution occurs through the appearance of genetic variation, its spread through populations by natural selection, and reproductive isolation leading to speciation.
Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.There are few mechanisms through which this process can be well understood.
The process by which a new species develops from the existing species is known as speciation.
Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.
A species can be defined as one or more populations of interbreeding organisms that are reproductively isolated in nature from all other organisms.
When populations no longer interbreed, they are thought to be separate species.
There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, Parapatric, and sympatric.
Speciation may also be induced artificially, through animal husbandry, agriculture, or laboratory experiments.
Allopatric speciation: It is regarded as the most common type of speciation. It involves the physical separation of a species into two groups. This may occur due to climatic changes, movement of tectonic plates leading to the fragmentation of a mass of land, or eruption of a land mass, formation of waterways, or due to the presence of an impassable mountain range.
Parapatric mode of speciation: It occurs due to partial spatial isolation of populations, and is characterized by a small overlap in their ranges as well as significant gene flow amongst the populations. However, the gene flow reduces due to changes in the local conditions, and the two populations become reproductively isolated.
Sympatric mode of speciation: It involves the formation of new species due to a genetic divergence among a few members of the species inhabiting a single geographic area. Unlike the other modes of speciation, here genetic divergence does not arise due to increase in geographic distance, but occurs within the same niche.
Peripatric speciation was Proposed by Ernst Mayr. In this type of speciation, a small group of members inhabiting a peripheral region of the range undergo reproductive isolation to form a new species. Many a time, it is considered to be a variation of allopatric speciation.
To determine the variation and the limitation between species, many concepts have been proposed.
When a taxonomist study a particular taxa, he/she must adopted a species concept and provide a species limitation to define this taxa.
Plant kingdom as other living kingdoms has a hierarchy structure ends mostly with species rank.
Species are one of the basic units to compare in almost all fields of biology.
A species is defined as the largest group of organisms in which two individuals are capable of reproducing fertile offspring, typically using sexual reproduction.
Definition of a species as a group of interbreeding individuals cannot be easily applied to organisms that reproduce only or mainly asexually.
If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species?
Idea of a species is something that we humans invented for our own convenience.
‘‘No matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as distinguish a species permanently; one species never springs from the seed of another nor vice versa” - JOHN RAY.
Used a sexual system ‘‘natural system” for defining species - LINNAEUS.
‘‘A species is a collection of all the individuals which resemble each other more than they resemble anything else, which can by natural fecundation produce fertile individuals, and which reproduce themselves by generation, in such a manner that we may from analogy suppose them all to have sprung from one single individual” - DE CANDOLLE.
This document will help you and will clear your concepts about the terms of Orthogenesis, Allometry & Adaptive Radiations, which are usually studied in evolution.
1.Definition and basic concepts of Biosystematics, , Historical perspectives of Biosystematics and Taxonomy, Stages of taxonomic procedures-alpha taxonomy, Beta taxonomy and Gamma taxonomy,
Neo taxonomy.
This presentation is uploaded by Mahar Tanvir ul Hassan Tibbi Tarhana Samandry Faisalabad Pakistan. I am enrolled in University of Sargodha in MSc Zoology.
Organisms are classified into a hierarchical classification that groups closely related individuals.
The species is the basic biological unit around which classifications are based.
TO FOLLOW THESE SLIDES you will learn about the adaptive radiations involve in evolution .
yo will learn about the parallel adaptations and its types
speciation role in the evolution
factors
key innvations
to imrove the article involving examples
Founder events
Adaptive plasticity
process of adaptive radiation
Factors promote adaptive radiations
Factors underlying adaptive radiations
defined by 0.S OSBORN
ecological space
geological
climatological
Islands
examplrs: 1.Darwin Finches 2.Cichlid fish genome -adaptive evolution, Stanford scientists
3.Anolis Lizards
Factors promote adaptive radiations
1.Generally speaking, adaptive radiations occur when new, unoccupied ecological niches become accessible to a founder population.
This can happen after a mass extinction during which the previous occupiers of those niches died out.
t can also happen when a colonizing species arrives at an island. (For instance the ancestor of the honeycreepers in Hawaii, or of Darwin's "finches" in the Galapagos)
Honey creeper
Change feeding habitat
At least 56 species of Hawaiian honeycreepers known to have existed, although all but 18 of them are now extinct.
Lack of competition. When a species enters an adaptive zone, it is poorly equipped to compete with species that have become adapted to the same niche.
For example, mudskippers are fish that are making a living on land, but they are marine fish and they don't have to compete against frogs and salamanders, which are restricted to fresh water. That is why we don't see freshwater mudskippers.
process of adaptive radiation
Ecological Release Colonization of species.
Taxon cycle
Habitat varying as population expand- species dispersal.
Adaptive plasticity Phenotypic plasticity(behavior change)
Property of an individual or genotype that may be adaptive, maladaptive or neutral with regard to an individual's fitness.
The particular way an individual's (or genotype's) phenotype varies across environments can be described as a reaction norm (Single genotype-phenotypic expression)
Speciation in adaptive radiation Founder events
Classical and molecular taxonomic parameters, species concept, systematic gradation of animals, nomenclature, modern scheme of animal classification into sub-Kingdom, division, section, phyla and minor phyla
Molecular evolution, four class of chromosomal mutation, Negative Selection and Positive Selection, Mutations in DNA and protein, Neutral Theory of Molecular Evolution, Evidence supporting neutral evolution, Phylogenetic trees, Methods of Tree reconstruction
Speciation is the evolutionary process by which reproductively isolated biological populations evolve to become distinct species.There are few mechanisms through which this process can be well understood.
The process by which a new species develops from the existing species is known as speciation.
Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.
A species can be defined as one or more populations of interbreeding organisms that are reproductively isolated in nature from all other organisms.
When populations no longer interbreed, they are thought to be separate species.
There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, Parapatric, and sympatric.
Speciation may also be induced artificially, through animal husbandry, agriculture, or laboratory experiments.
Allopatric speciation: It is regarded as the most common type of speciation. It involves the physical separation of a species into two groups. This may occur due to climatic changes, movement of tectonic plates leading to the fragmentation of a mass of land, or eruption of a land mass, formation of waterways, or due to the presence of an impassable mountain range.
Parapatric mode of speciation: It occurs due to partial spatial isolation of populations, and is characterized by a small overlap in their ranges as well as significant gene flow amongst the populations. However, the gene flow reduces due to changes in the local conditions, and the two populations become reproductively isolated.
Sympatric mode of speciation: It involves the formation of new species due to a genetic divergence among a few members of the species inhabiting a single geographic area. Unlike the other modes of speciation, here genetic divergence does not arise due to increase in geographic distance, but occurs within the same niche.
Peripatric speciation was Proposed by Ernst Mayr. In this type of speciation, a small group of members inhabiting a peripheral region of the range undergo reproductive isolation to form a new species. Many a time, it is considered to be a variation of allopatric speciation.
To determine the variation and the limitation between species, many concepts have been proposed.
When a taxonomist study a particular taxa, he/she must adopted a species concept and provide a species limitation to define this taxa.
Plant kingdom as other living kingdoms has a hierarchy structure ends mostly with species rank.
Species are one of the basic units to compare in almost all fields of biology.
A species is defined as the largest group of organisms in which two individuals are capable of reproducing fertile offspring, typically using sexual reproduction.
Definition of a species as a group of interbreeding individuals cannot be easily applied to organisms that reproduce only or mainly asexually.
If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species?
Idea of a species is something that we humans invented for our own convenience.
‘‘No matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as distinguish a species permanently; one species never springs from the seed of another nor vice versa” - JOHN RAY.
Used a sexual system ‘‘natural system” for defining species - LINNAEUS.
‘‘A species is a collection of all the individuals which resemble each other more than they resemble anything else, which can by natural fecundation produce fertile individuals, and which reproduce themselves by generation, in such a manner that we may from analogy suppose them all to have sprung from one single individual” - DE CANDOLLE.
This document will help you and will clear your concepts about the terms of Orthogenesis, Allometry & Adaptive Radiations, which are usually studied in evolution.
1.Definition and basic concepts of Biosystematics, , Historical perspectives of Biosystematics and Taxonomy, Stages of taxonomic procedures-alpha taxonomy, Beta taxonomy and Gamma taxonomy,
Neo taxonomy.
This presentation is uploaded by Mahar Tanvir ul Hassan Tibbi Tarhana Samandry Faisalabad Pakistan. I am enrolled in University of Sargodha in MSc Zoology.
Organisms are classified into a hierarchical classification that groups closely related individuals.
The species is the basic biological unit around which classifications are based.
TO FOLLOW THESE SLIDES you will learn about the adaptive radiations involve in evolution .
yo will learn about the parallel adaptations and its types
speciation role in the evolution
factors
key innvations
to imrove the article involving examples
Founder events
Adaptive plasticity
process of adaptive radiation
Factors promote adaptive radiations
Factors underlying adaptive radiations
defined by 0.S OSBORN
ecological space
geological
climatological
Islands
examplrs: 1.Darwin Finches 2.Cichlid fish genome -adaptive evolution, Stanford scientists
3.Anolis Lizards
Factors promote adaptive radiations
1.Generally speaking, adaptive radiations occur when new, unoccupied ecological niches become accessible to a founder population.
This can happen after a mass extinction during which the previous occupiers of those niches died out.
t can also happen when a colonizing species arrives at an island. (For instance the ancestor of the honeycreepers in Hawaii, or of Darwin's "finches" in the Galapagos)
Honey creeper
Change feeding habitat
At least 56 species of Hawaiian honeycreepers known to have existed, although all but 18 of them are now extinct.
Lack of competition. When a species enters an adaptive zone, it is poorly equipped to compete with species that have become adapted to the same niche.
For example, mudskippers are fish that are making a living on land, but they are marine fish and they don't have to compete against frogs and salamanders, which are restricted to fresh water. That is why we don't see freshwater mudskippers.
process of adaptive radiation
Ecological Release Colonization of species.
Taxon cycle
Habitat varying as population expand- species dispersal.
Adaptive plasticity Phenotypic plasticity(behavior change)
Property of an individual or genotype that may be adaptive, maladaptive or neutral with regard to an individual's fitness.
The particular way an individual's (or genotype's) phenotype varies across environments can be described as a reaction norm (Single genotype-phenotypic expression)
Speciation in adaptive radiation Founder events
Classical and molecular taxonomic parameters, species concept, systematic gradation of animals, nomenclature, modern scheme of animal classification into sub-Kingdom, division, section, phyla and minor phyla
Molecular evolution, four class of chromosomal mutation, Negative Selection and Positive Selection, Mutations in DNA and protein, Neutral Theory of Molecular Evolution, Evidence supporting neutral evolution, Phylogenetic trees, Methods of Tree reconstruction
It states that the present day complex plants and animals have evolved from earlier simpler forms of life by gradual changes. SEQUENTIAL EVOLUTION ,DIVERGENT EVOLUTION, Theories of evolution.
This is PPT on Evolution. This is just and introductory PPT. Soon There will be a PPT with much more on Evolution. Hope That you all like it. please like and share. each like Counts.
This is PPT on Evolution. This is just and introductory PPT. Soon There will be a PPT with much more on Evolution. Hope That you all like it. please like and share. each like Counts.
its deals with the general basic ideas of gene and evolutions.different types of examples are used to explain the gene and evolutions.the origin of basic genetics and their ideas are also formulated in this presentation
SOMEONE HELP Complete sentences, stating the differences and relati.pdfexpressionnoveltiesk
SOMEONE HELP: Complete sentences, stating the differences and relationships between the
two terms, and give specific examples where appropriate.
1. gene flow / genetic drift
2. sexual selection / artificial selection
3. ring species / biological species concept
4. hybrid inviability / temporal isolation
5. autopolyploidy / allopatric speciation
6. molecular clock / cladogram
7. gradualism / uniformitarianism
8. extreme thermophiles / viroids
9. HIV / Creutzfeld-Jakob disease
10. biofilm / microbial fuel cell
Solution
Q.No 1
Genetic drift is a mechanism of evolution of biological species that takes place because of the
change in the frequency of alleles in a population. These changes in the allele frequency in a
population occur randomly. One very common example to describe the genetic drift would be
that most of the human families have different number of boys and girls, as the X or Y alleles
have been passed differently into the new generation from the parents. Although the X and Y
alleles do not really contribute for the evolution, the frequency changes in other alleles would
have a considerable effect for evolution.
Gene flow is a process of evolution that takes place when genes or alleles move from one
population to another. It is also known as the Gene Migration, and that could cause changes in
the allele frequency as well as some variations in the gene pool of both populations. There are
some good examples to support this phenomenon from humans regarding a developed immunity
for malaria among new Western Africans after their parents mated with Europeans who initially
had the immunity. It is interesting to notice that gene flow could take place between two species,
as well.
Q.No 2
Sexual selection enhances mating success or the number of copulations, while natural selection
tends to produce well-adapted individuals to their environment. Sexual selection does not adapt
the individuals to their environment. Unlike sexual selection, natural selection acts on traits
which increase the fitness of members in a population. Certain adaptations have been derived
from the sexual selection which could never have been arisen from natural selection alone (Ex:
the neck of the giraffe, various plumages of most male birds etc.). Generally sexual selection
depends on the success of one sex while natural selection depends on the success of both sexes in
relation to the general condition of life. In most of the animals, certain traits related to their
sexual selection process do not express their characteristics until the organism is able to mate,
but naturally selected traits may occur at birth of the organism during the process of natural
selection.
Q.No 3
A ring species is a connected series of neighbouring populations, each of which can interbreed
with closely sited related populations, but for which there exist at least two \"end\" populations in
the series, which are too distantly related to interbreed, though there is a potential gene flow
between e.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
Ethnobotany and Ethnopharmacology:
Ethnobotany in herbal drug evaluation,
Impact of Ethnobotany in traditional medicine,
New development in herbals,
Bio-prospecting tools for drug discovery,
Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
ESC Beyond Borders _From EU to You_ InfoPack general.pdf
Neodarwinism or synthetic theory of evolution
1. Assignment Of
Evolutionary Biology And
Biodiversity
Topics – Neo-Darwinism
Natural selection
Mutation And Recombination
Presented By- Sakshi
2. Neo-DarwinismNeo-Darwinism is a modified version of
the theory of natural selection and is
a sort of reconciliation between Darwin
and de varies theory.
Scientist contributed to this theory –
Huxley,
R.A.Fischer
etc.
3. Postulates of Neo-Darwinism
1. Genetic variability – variability is an opposing
force to heredity.
Forms the raw material for evolution.
Various sources of genetic variability-
1. Chromosomal aberrations- Morphological changes in
chromosomes without affecting their number.
o These are of four types-
A. Deletion – loss of gene block from chromosome.
B. Duplication – presence of some genes more than once.
4. C. Translocation- transfer of gene block from one chromosome to other.
D. Inversion- rotation of intercalary gene block through 180 degrees.
5. 2. Numerical chromosomal changes-
a. Eulpoidy – gain or loss of one or more genome. It may be-
Haploidy or polyploidy
b. Aneuploidy- gain or loss of one or two chromosomes. It may
be hypoploidy and hyperploidy.
6. 3. Gene Mutations- invisible changes in the chemical nature of the
gene. These include- Point mutation.
.Gross mutations.
Deletion.
Addition.
Substitution.
4. Recombination of genes- new combination of genes are formed
due to crossing over , chance arrangement of the bivalents during
metaphase and chance fusion of gametes.
5. Hybridization- the interbreeding of two different individuals to
produce hybrids.
Introduces genes from one species to the gene pool of other species.
7. 6. Mutagens- physical and chemical agents used to induces
mutations artificially.
A. chemical mutagens- such as base analogues , methylating agents ,
acridine dyes etc.
B. Physical mutagens- such as temperature, x-rays ,uv-rays etc.
7. Genetic Drift- change in the gene frequency of small breeding
population due to bottle neck and founder effect.
FOUNDER EFFECT-
8. Immigration- introduces many genes in the existing gene pool by
cross breeding between the native individuals and immigrants.
8. 2. Natural selection-
Does not operate on survival of the fittest.
Operates through Differential Reproduction and comparative reproductive
success.
Differential Reproduction- members which are better adapted to
environment reproduce at a high rate and produce more offsprings than the
members which are less adapted.
Due to sexual communication, there is free flow of genes and the genetic
Variability spreads from individuals to deme then to population and finally in
most of the members of species.
So, natural selection causes progressive changes in the gene frequency.
Frequency of more adaptive genes increases and that of less adapted gene
decreases.
10. 3. Reproductive Isolation- the inability of living
organisms to interbreed.
Maintains distinctivnesss of characters
among species.
1. Mechanical isolation- due to the difference in the morphology of genitalia or
reproductive organs.
2. Geographical Isolation- due to physical factors like sea, mountain, deserts
etc.
11. 3. Spatial isolation- individuals are isolated by long
distances.
4. ecological or habitat isolation- due to differences in their
habitat.
5.Temporal Isolation- due to difference in the breeding periods
in different seasons of the year.
6. Ethological or Behavioural isolation- due to behavioural
differences between individuals of different species during
courtship.
12. 7. Genetic Isolation – due to inter specific sterility due to
accumulation of independent gene mutations for structural and
functional characters.
8. physiological Isolation- due to functional incompatibility in
their mating or in production , fertilization and survival of the
gametes.
13. So according to Neo Darwinism, 4 steps of
organic evolution are-
1. Appearance of genetic variability in certain members of a
population.
2. Spread of genetic variability over population by differential
reproduction.
3. Some sort of reproductive isolation between elementary
species and the parental species.
4. Accumulation of genetic variability leads to speciation.
14. NATURAL SELECTION
The process by which comparatively better adapted individuals out
of a heterogenous population are favoured by the nature over the
less adapted individuals.
Mechanism-
It operates through differential reproduction.
Differential reproduction states that the individuals which
are better adapted to environment reproduce at a higher rate and
produce more offsprings than the individuals which are less adapted.
So contribute more to the gene pool.
15. Due to sexual communication there is free flow of genes and
the genetic variability which appears in certain individuals
spreads from one deme to other and to population and finally
in most of the members of the species.
So natural selection causes progressive changes in the gene
frequencies. The frequency of the more adaptive gene increases and
that if less adapted gene decreases.
17. 2. Sickle cell anemia-
Persons with sickle cell anemia are found in the tropical areas of the
Africa where malaria is very common because sickle shaped cell kill
the malarial parasite.
Thus natural selection has preserved it along with the normal
haemoglobin in the malaria affected areas.
18. Types Of Natural Selection-
1. Stabilizing or Balancing Selection-
Under stabilizing selection, extreme varities from both the
ends of frequency distribution are eliminated.
Favours the average or normal phenotype.
Bell shaped curve.
E.g.- sickle cell
Anemia.
19. 2.Directional Selection-
Population changes towards one particular direction along
with the change in environment.
Individuals at one extreme are eliminated while individuals
at the other extreme are favoured. E.g.- Industrial
melanism, DDT resistant mosquitoes.
20. 3. Disruptive Selection-
Favours extreme expression of certain traits to increase the
variance in the population.
Breaks a homogeneous population into many adaptive forms.
Results in balanced polymorphism.
22. RECOMBINATION
Recombination is the process by which two DNA molecules exchange
genetic information resulting in the production of new combination
of alleles.
It creates the genetic diversity at the level of genes and leads to
variation.
23. In eukaryotic cell the, recombination occurs during the
pachytene substage of meiosis1.
Recombination may also occur during mitosis in eukaryotes ,
where it ordinarily involves the two sister chromosomes forms
after chromosomal replication.
Types of Recombination
1. Homologous Recombination
Genetic recombination in which nucleotide sequences are
exchanged between two similar or identical DNA
molecules.
24. Mostly used by the cells to accurately repair harmful
breaks that occur on both strands of DNA known as
double strand break.
No net gain or loss of nucleotides.
25. HOLIDAY JUNCTION
Corresponding strands of two aligned homologous DNA duplexes
are nicked by Endonuclease.
The nicked strands cross over to pair with the nearly
complementary strands of the homologous duplex after which
the nicks are sealed with the non sister chromatid of the
homologous chromosome with the help of the enzyme Ligase.
26. 2.NON-HOMOLOGOUS OR ILLEGITIMATE
RECOMBINATION-
Occurs in the region where no large scale sequence similarity
is apparent.
3.SITE-SPECIFIC RECOMBINATION-
Occurs between particular short sequences about 12-24kb.
27. Takes place in the segments of DNA strands possessing
only limited degree of sequence homology.
4. REPLICATIVE RECOMBINATION-
A type of recombination which generates new copy
of the segment of DNA.
28. RECIPROCAL RECOMBINATION-
Equal exchange of genetic information.
Resulting in new DNA molecules that carry the genetic information
derived from both the parents.
The number of alleles remain the same only their arrangement has
changed.
NON-RECIPROCAL RECOMBINATION/ GENE
CONVERSION-
One way transfer of the genetic information.
Number of alleles has changed.
Transfer of the genetic material from a donar to a highly homologous
acceptor sequence.
29. ADVANTAGES
1.Enhances genetic diversity in a population –like new gene or allele
combination.
2. Negative selection can remove deleterious alleles from a
population without removing the entire chromosome.
3.Ensures proper segregation of homologous chromosome.
4.Ensures the genetic stability of organism.
5. Site specific recombination system are potent modifiers.
6.It is used to map the genes on chromosome as the recombination
proportional to the distance between the genes.
7.Used for making transgenic cells and organism.
30. MUTATION
Sudden heritable changes in the genetic material or character of
organism.
Individuals showing mutation are called mutant.
The agents causing mutation are called mutagens.
TYPES OF MUTATIONS
1. SPONTANEOUS MUTATION-
Occurs naturally without a known cause.
2. Induced mutation- Resulting from the exposure of
organisms to mutagenic agents like ionizing radiation, uv light and
various chemicals.
31. BASED ON THE TISSUE OF ORIGIN-
1. SOMATIC MUTATION-
Occurs in the somatic cells.
In asexually reproducing species , somatic mutations transmits from one progeny
to next progeny.
2. GERMINAL MUTATIONS-
Occurs in the gametic cells .
Transmitted from one generation to the next gnenration.
BASED ON THE DIRECTION-
1.FORWARD MUTATION
Occurs from the normal type to mutant allele.
32. 2.REVERSE MUTATION-
Occur from the mutant allele to a normal type.
CHROMOSOMAL MUTATIONS-
Changes occur in the number and structure of chromsome.
These include-
1. CHROMOSOMAL ABERRATIONS-
MORPHOLOGICAL CAHNGES IN THE CHROMOSOME WITHOUT
AFFECTING THEIR NUMBER.
It is of 4 types-
1. DELETION- Loss of gene block from the chrosome. It may be
terminal or intercalary.
2. DUPLICATION- Presence of some genes more than once. It may be
tandem or reverse.
33. C. Translocation- transfer of gene block from one chromosome
to other.
D. Inversion- rotation of intercalary gene block through 180
degrees.
34. 2. Numerical chromosomal changes-
a. Eulpoidy – gain or loss of one or more genome. It may be-
Haploidy or polyploidy
b. Aneuploidy- gain or loss of one or two chromosomes. It may
be hypoploidy and hyperploidy.
35. GENE MUTATIOINS
Invisible changes in the chemical nature of the gene.
Many times a gene mutation does not produce any detectable
phenotypic effect as most of the gene mutations are recessive. But
the dominant gene mutations in homozygous condition may produce a
phenotypic change.
The gene mutations are of three types:
1. Frame shift mutations.
2. Substitutions mutations.
3. Point Mutations.
36. 1. Frame Shift mutations:
Mutations in which the reading of the frame of base
sequences shifts laterally either in the forward direction due
to insertion and in backward direction due to deletion
So these are of two types-
1. INSERTION- One or more nucleotides are added in the
segment of DNA representing cistron or gene.
2. DELETION- one or more nucleotides are lost from the
segment of DNA representing a cistron or gene.
37. 2. SUBSTITUTION MUTATION-
In a substitution, a nitrogen base is changed with another
E.g.- In Sickle cell anemia , glutamic acid of B-chain of Hb-a is replaced by valine
amino acid to form defective Hb-s.
These are of two types-
1. Transition- purine is replaced by purine and a pyrimidine is replaced by a
pyrimidine.
2. Transversion- Purine is replaced by pyrimidine or vice-versa.
-
38. 3. POINT MUTATIONS-
A point mutation is a change in single nucleotide.
It is of two types-
1. SYNONYMOUS MUTATION-
Replaces a codon with another codon that codes for the same amino
acid .So the produced amino acid sequence is not modified.
2. NON-SYNONYMOUS MUTATION-
Replaces a codon with another codon that codes for a different amino
acid, so their amino acid sequence is altered.
These are of two types-
39. 1. MISSENSE MUTATION-
These changes a nucleotide to cause substitution of different amino
acid . Thus in turn can render the resulting protein nonfunctional.
2. NON-SENSE MUTATION-
Point mutation that Results in a premature stop codon, or a non-sense codon
In the transcribed mRNA and possibly a truncated and often nonfunctional
protein product.
