MUTATION.pptx

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

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.

10. 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.

11. TYPES OF FRAME SHIFT MUTATION

12. INDUCED MUTATION Physical Mutagens Chemical Mutagens

13. 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.

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

15. 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.

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

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

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

19. 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.

20. 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.

21. AMES TEST

22. DETECTION OF MUTATION IN DROSOPHILA

23. 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.

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