2. Introduction
• Sudden heritable change in genetic material or character of an
organism due to alteration in nucleotide sequence is known as
mutation.
• Individuals showing these changes are known as mutants.
• Different types of genes produced by mutation called alleles.
• Factor or agents causing mutation are known as mutagens.
• Mutation which causes changes in base sequence of a gene are
known as gene mutation or point mutation.
• This alteration occurs by chemical or physical means or
spontaneously.
3. Characteristics of Mutation
• Most mutations have harmful effect, but some mutations
are beneficial
• Spontaneous mutations occurs at very low rate
• Some genes shows high rate of mutation such genes are
called as mutable gene
• Highly mutable sites within a gene are known as hot spots
• Mutation can occur in any tissue/cell (somatic or germinal)
of an organism
4. Classification of mutation
Based on the survival of an individual
Based on causes of mutation
Based on tissue of origin
Based on direction of mutation
Type of trait affected
5. Based on the survival of an individual
1. Lethal mutation – when mutation causes death of all
individuals undergoing mutation are known as lethal
2. Sub lethal mutation - causes death of 90% individuals
3. Sub vital mutation– such mutation kills less than 90%
individuals
4. Vital mutation -when mutation don’t affect the survival of a
individual are known as vital
5. Supervital mutation – This kind of mutation enhances the
survival of individual
6. Based on causes of mutation
1. Spontaneous mutation-
Spontaneous mutation occurs naturally without any cause. The
rate of spontaneous mutation is very slow eg- Methylation followed by
deamination of cytosine.
Rate of spontaneous mutation is higher in eukaryotes than
prokaryotes.
Eg. UV light of sunlight causing mutation in bacteria
2. Induced Mutation-
Mutations produced due to treatment with either a chemical or
physical agent are called induced mutation .
The agents capable of inducing such mutations are known as mutagen.
Use of induced mutation for crop improvement program is
known as mutation breeding.
Eg. X- rays causing mutation in cereals
7. Based on tissue of origin
1. Somatic mutation-
A mutation occurring in somatic cell is called somatic mutation.
In asexually reproducing species somatic mutations transmits from
one progeny to the next progeny
2. Germinal Mutation-
When mutation occur in gametic cells or reproductive cells are known
as germinal mutation.
In sexually reproductive species only germinal mutation are
transmitted to the next generation
8. Based on direction of mutation
1. Forward mutation-
When mutation occurs from the normal/wild type allele to mutant
allele are known as forward mutation
2. Reverse mutation-
When mutation occurs in reverse direction that is from mutant
allele to the normal/wild type allele are known as reverse muta
Type of trait affected
1. Visible mutation- Those mutation which affects on phenotypic
character and can be detected by normal observation are known as visible
mutation
2. Biochemical mutation- mutation which affect the production of
biochemicals and which does not show any phenotypic character are known
as biochemical mutation ion
9. Different types of Mutation
• Mutation is divided into following types
Point Mutation
Frame shift Mutation
Multistage Mutation
Induced Mutation
Spontaneous Mutation
10. 1. Point Mutation
• Substitution of one nucleotide by another nucleotide at specific
nucleotide sequence of gene called point mutation.
• This substitution is of two types:
Substitution of one purine by another purine ( A by G) and one
pyrimidine by another pyrimidine ( T or U by C) known as
Transition type mutation.
Replacement of purine by pyrimidine known as Transversion
This substitution result in three mutaion
1. Missense- triplet code is altered to specify amino acid
different from normally located at particular position in
protein.
11. 2. Non-sense - deletion of nucleotide within gene cause
premature polypeptide chain termination by producing
non- sense codon .
3. Neutral – altered gene triplet produce m-RNA codon
which same as amino acid .
12. 2. Frame shift Mutation
• It results in addition or loss of one or more nucleotides in
gene termed as insertion or deletion mutation respectively.
• It shift reading frame shift & synthesize new amino acid.
3. Multisite Mutation
• Chromosomal rearrangement such as inversion, duplication,
deletion.
13. • Mutagens are physical or chemical agents that increase rate
of mutation call induced mutation.
• Mutation of every gene varies from each other e.g Insulin
gene & interferon gene mutation varied from each other.
• Mutation rate is average number of mutations per cell
division. For any single gene it is ranges between 10-3 and 10-9
per cell division.
• Mutagens are of two types
Physical
Chemical
4. Induced Mutation
14. Physical Mutagen-
• Eg. UV rays, X-rays, gamma rays, heat etc.
• All cause non sensitive mutation
• Some cases due this mutant it cause change in few bases of
DNA . And cause damage of DNA and micro-organism get kill or
destroyed.
Chemical mutagen-
• Eg. Nitrous acid, ethyl acetate alkylating agents alcohols etc.
• In this process during DNA replication cause replacement of
bases with another bases (Transition &Transversion) type
mutation cause mispairing & mutation.
• And cause damage of DNA and micro-organism get kill or
destroyed.
15. 5. Spontaneous Mutation
• Mutation occurs in absence of mutagenic agent called
spontaneous mutation.
• It is independent of environment. Explain by fluctuation test.
• They found that fluctuation occurs in number of
bacteriophage resistant colonies in small volume culture
compare to large volume culture.
• Observe that number of resistant mutant fluctuated from
sample to sample prior to exposure to phage.
• Conclude that mutation in bacteria occurs spontaneously.
16.
17. • The result of fluctuation test was again elaborated by
using replica plate technique.
• Questions
1. Define mutation & its type. 5 M
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