1. Mutation is a permanent alteration in the DNA sequence that makes up a gene or chromosome. There are several types of mutations including point mutations, frameshift mutations, deletions, duplications, inversions, and translocations.
2. Point mutations involve a change to a single nucleotide base, such as a substitution, insertion or deletion. Frameshift mutations occur when multiple nucleotides are inserted or deleted, changing the reading frame.
3. Mutations can be caused by errors during DNA replication or by environmental mutagens like radiation or chemicals. They can occur in somatic cells or germ cells and be transmitted to offspring. Most mutations are harmful but some can provide benefits for adaptation or evolution.
2. Introduction
• Sudden heritable change in genetic material or character of an organismis
known as mutation
• Individuals showing these changes are known as mutants
• An individual showing an altered phenotype due to mutation are knownas
variant
• Factor or agents causing mutation are known as mutagens
• Mutation which causes changes in base sequence of a gene are knownas
gene mutation or point mutation
3. A mutation is the permanent alteration of the nucleotide
sequence of the genome of an organism, virus, or extra
chromosomal DNA or other genetic elements.
Mutations result from errors during DNA replication or other
types of damage to DNA
The two main causes of mutation are
MISTAKES IN CELLREPLICATION
During replication of DNA, double strands of DNA are separated.
Each strand is then copied to become another double strand. About 1
out of every100,000,000 times, a mistake occurs during copying,
which can lead to a mutation.
4. ENVIRONMENTAL FACTORS
. Mutations can also be caused by environmental foes. Tobacco,
ultraviolet light and other chemicals (Hydroxylamine
Base analogs etc ) Alkylating agents are all potential
enemies of DNA
These agents cause the DNA to break down. This is not
necessarily unnatural — even in the most isolated and pristine
environments, DNA breaks down.
5. History
• English farmer Seth Wright recorded case of mutation first time in 1791 in
male lamb with unusual short legs.
• The term mutation is coined by Hugo de Vries in 1900 by his observation in
Oenothera.
• Systematic study of mutation was started in 1910 when Morgan
genetically analyzed white eye mutant of Drosophila.
• H. J. Muller induced mutation in Drosophila by using X- rays in 1927 ; he
was awarded with Nobel prize in 1946.
6. Characteristics of Mutation
• Generally mutant alleles are recessive to their wild type or normal alleles
• 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 hotspots.
• Mutation can occur in any tissue/cell (somatic or germinal) of an organism
7. Classification of mutation
• 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 an individual are
known as vital
5. Supervital mutation – This kind of mutation enhances the survival of
individual
8. • 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
9. • 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
progeny to the next progeny
2. Germinal Mutation-
from one
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
10. • 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 mutation
11. • Type of trait affected
1. Visible mutation- affects on
phenotypic character
Those mutation
and can be
which
detected by normal
observation are known as visible mutation
2. Biochemical mutation- mutation which affect the production
of biochemicals and which does not not show any
phenotypic character are known as biochemical mutation
14. . A chromosome aberration, or mutation
is a missing, extra, or irregular portion of chromosomal
DNA. It can be from an atypical number of chromosomes or
a structural abnormality in one or more chromosomes.
There are many types of chromosome anomalies. They can
be organized into two basic groups, numerical and
structural anomalies.
15. Numerical disorders
This is called aneuploidy (an abnormal number of
chromosomes), and occurs when an individual
either is missing a chromosome from a pair(
monosomy) or has more than two chromosomes of
a pair
(trisomy, tetrasomy etc.).
In humans, an example of a condition caused by
a numerical anomaly is Down Syndrome, also
known as Trisomy 21
18. ii. Structural abnormalities
. When the chromosome's structure is
altered, this can take several forms:
1. DELETION
2. DUPLICATION
3. INVERSION
4. TRANSLOCATION
26. Nondisjuncti
on• Failure of chromosomesto
separate duringmeiosis
• Causes gamete to have too many
or too few chromosomes
• Disorders:
– Down Syndrome –
– Turner Syndrome –
– Klinefelter’s Syndrome –
27. A gene mutation is a permanent alteration
in the DNA sequence that makes up a
gene, such that the sequence differs from
what is found in most people.
Mutations range in size; they can affect
anywhere from a single DNA building
block (base pair) to a large segment of a
chromosome that includes multiple genes.
28. Gene mutations are heritable changes in the base
sequence of individual genes or genomic DNA ,which
may produce allelic alterations in the genotype.
Since they occur within indl genes,they are also
called intragenic mutations or point mutations in
distinction with chromosome mutations(changes in
chromosome structure.) and genome mutations
(changes in chromosome number) .
The frequency of spontaneous gene mutations
increased by several factors.
Defective DNA repair system
defective DNA replication system
Defective DNA polymerases and DNA ligase
production of aberrant DNA precrsors.
29. POINT MUTATION A point mutation is a
type of mutation that causes a single nucleotide base
substitution, insertion, or deletion of the genetic
material, DNA or RNA.
Causes of point mutations
Causes of point mutations
Point mutation is a random SNP (single-nucleotide
polymorphism) mutation in the DNA.
A single point mutation can change the whole DNA
sequence.
spontaneous mutations that occur during DNA
replication.
The rate of mutation may be increased by mutagens
30.
31. . Functional categorization
Nonsense mutation:
Code for a stop, which can truncate the protein. A
nonsense mutation converts an amino acid codon
into a termination codon. This causes the protein to
be shortened because of the stop codon interrupting
its normal code.base pair subtitution-
Missense mutation:
It is a point mutation in which a single nucleotide
change results in a codon that codes for a different
amino acid.
It is a type of nonsynonymous substitution
32. .S.ilent mutations:
Code for the same amino acid. A silent mutation has no
effect on the functioning of the protein. A single
nucleotide can change, but the new codon specifies the
same amino acid, resulting in an unmutated protein.
This type of change is called synonymous change,
since the old and new codon code for the same amino
acid.
33. Types of Gene
Mutations• Include:
–Point Mutations Affect only the
indl genes located in small portions
of chromosomes,hence the name
– Base pair Substitutions
–Insertions
–Deletions
–Frameshift
34. Point
Mutation
• Change of a single
nucleotide
• Includes the deletion,
insertion, or
substitution of ONE
nucleotide in a gene
36. Gene mutations are classified under two
general classes-frame –shift mutation
and base-pair substitutions.
fewer than 20% of the spontaneous
mutations are due to base-pair
substitutions. mostly by frame shift
mutation.
37. Frameshift
Mutation
• Inserting or deleting one or
more nucleotides
• Changes the “reading frame”
like changing a sentence
• Proteins built incorrectly
38. A frameshift mutation (also called a
framing error or a reading frame shift) is a genetic
mutation caused by indels (insertions or deletions) of a
number of nucleotides in a DNA sequence that is not
divisible by three.
39. Frame shift mutation-or sign mutation or reading
frame mutation are gene mutations which bring about
a shift in the reading frame of codons through
changes in the no and order of nucleotides(base
pairs) .
They involve insertion or deletion of one or more
nucleotide pairs.Non-functional enzymes produced
.More deleterious than sustitution mutations.
40. Base-pair substitution mutation-are the mutations in which one
kind of nitrogenous base of a codon of DNA or mRNA is
substituted by another kind.or by a base derivative.
Some sbstitution mutation generate non-sense codons ,which
will not specify any amino acids,but will serve as terminator
codons. such substitution mutation are called non-sense
mutations.
Spontaneous base pair substitution occur by 3 processes
Tautomerization,ionization,binding of base analogue.Ionization-
of bases during DNA replication introduce transitional base
pairs.It involves the lose of hydrogen atoms from the base.
Transversion –purine replced by pyramidine.
Transition—Purine replaced by purine .this is caused by
Tautomerization,Base analogue,Deamination.
42. Deletion mutation is a mutation in which
a part of a chromosome or a sequence of DNA is lost
during DNA replication.
Deletions can be caused by errors in
chromosomal crossover during meiosis , which
causes several serious genetic diseases. e.g.
Williams syndrome.
Small deletions are less likely to be fatal; large
deletions are usually fatal
44. Insertion mutation is the addition of one or more
nucleotide base pairs into a DNA sequence.
Insertions can be particularly hazardous if they occur in an
exon, the amino acid coding region of a gene
