A mutation is a change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection.2

1. Dr. Rachana Choudhary
Department Of Microbiology
Shri Shankaracharya Mahavidyalya,Junwani Bhilai

2. SYNOPSIS
Introduction
History
Stages of Mutation
Occurrence of Mutation
Expression of Mutation
Suppressor Analysis
Detection of Mutation
Ames Test
Conclusion
Reference

3. INTRODUCTION
• A mutation can be define as “ a sudden and heritable
change in the nucleotide sequence of gene”.
• The term mutation is derive from a latin word
“mutare”.
• The heritable change includes change in gene structure or
composition.
• Therefore mutation is the result of stable and heritable
change in nucleotide sequence of DNA.

4. HISTORY
 The term mutation was given by “Hugo de
Vries” in “1880”.
 To describe the phenotype change in evening
primrose. (Oenthera Lamarckiana)

5. STAGES OF MUTATION
GERMINAL V/S SOMATIC MUTATION:-
• Mutation can occur any cell, they only affect the
future generations if they occur in the cells that
produce the gametes are “germinal” or “germ
line” mutation.
• Mutations in other cells are rarely noticed, except
in the case of cancer, where the mutated cell
proliferates uncontrollably. Mutation in cells other
than germ line cells are “somatic” mutations.

6. OCCRUENCE OF MUTATION
 The process of formation of a mutant
organism is known as “Mutagenesis”.
Mutagenesis arises by two mechanism:-
1) Spontaneous mutation.
2) Induced mutation.

7. ORIGIN OF SPONTANEOUS MUTATION
SPONTANEOUS
MUTATION
SUBSTITUTION
MUTATION
TRANSITION
MUTATION
TRANSVERSION
MUTATION
FRAME SHIFT
MUTATION
1)DELETION
2)INSERTION

8. A) SUBSTITUTION MUTATION
In substitution mutation a nitrogenous base of a
triplet codon of DNA is replaced by another
nitrogenous bases. Substitution mutation is of two
types:-
1)Transition mutation:-Transition involves
replacement of one purine in a polynucleotide
chain by another purine.
A C, C T

9.  Transition substitution occurs due to
tautomerisation during DNA replication
 In tautomeric state a nitrogenous base cannot
pair to its normal partners.
2)Tranversion mutation:-It involves the
substitution of a purine by pyrimide or
pyrimidine by a purine.
 The occurence of tranversion was postulated
by E.Freeze in 1959.

11. B)FRAME SHIFT MUTATION
 The mutation caused by the addition or
deletion of nitrogenous base in the DNA or
mRNA are known as frame shift mutation.
 These deletion or these addition may only a
few frame.

12. TYPES OF FRAME SHIFT MUTATION

13. INDUCED MUTATION
Physical
Mutagens
Chemical
Mutagens

14. INDUCED MUTATION
 Any agent which directly damages DNA
changes its chemistry with repair mechanism
will induced mutation and the agent which
cause such action are known s “mutagen”.
 Basically mutagen divided into two main
classes
A) Physical mutagen.
B) Chemical mutagen.

15. A) PHYSICAL MUTAGEN
1. RADIATION
Ionizing
radiation
Non- ionizing
radiation

16. 1. RADIATIONS
1.IONIZING RADIATION:-
It include produces break in chromosome and the break
in sugar phosphate backbone of polynucleotide strands.
Example:- X-rays.
X-rays cause breakage of phosphate ester linkage in
DNA.

17. 2. NON-IONIZING RADIATION
Example- UV-rays is responsible for causing DNA damage

18. B) CHEMICAL MUTAGEN
1) ALKYLATING AGENTS:- those chemicals addition
on alkyl groups to hydrogen bonding oxygen of
nitrogenous base is called as alkylating agent. E.g-
dimethyl sulphate.
2) DEAMMINATING AGENTS:- e.g- deamination of
adenine:- deamination of adenine result in the
formation of hypoxanthine.
3) INTERCALATING AGENTS:- due to intercalation,
DNA changes result in deletion or addition of base pair
after replicayion.
4) BASE ANALOGUE:-They are the derivatives of
nitrogenous bases in DNA.

19. EXPRESSION OF MUTATION
Point
mutation
Non-sense
mutations Missense
mutation
Silent
mutation

21. SUPRESSION MUTATION
• Occurs at sites different from the original mutation and
mask for the initial mutation without reversing it.
INTRAGENIC SUPRESSION:-It results from
suppressor mutation that occurs in the same genes as the
original mutation.
• Occur on the same codon.e.g, nearby addition restore a
delition.
INTERGENIC SUPRESSION:-Occur on a different
gene.
• Many function mRNA traslocation.

22. DETECTING MUTAGENS
• Radiations and certain chemical compounds
are”mutagens”.
• Cancer is caused by somatic mutations.
• Testing for mutagenecity is a key step is a development of
pharmaceutical drugs.
• Simple test using bacteria (Salmonella, a close relative of
E.coli) developed by Bruce Ames:the Ames test.

23. AMES TEST

24. DETECTION OF MUTATION IN DROSOPHILA

25. CONCLUSION
 Mutation important phenomenon as it is a
ultimate source of genetic variation provides the
raw material for evolution.
Thus mutation are essential to provide new
genetic variability for microbial evolution &
adaption.
But at the same time, if mutation occurred to
frequently then they would totally distrupt the
transmission of information from generation to
generation.

26. REFERENCES
Microbiology by R.C.
Dubey & Maheshwari.
 Microbiology by R.P. Singh
Genetics by P. K. Gupta
Biochemistry by J.L. Jain