TYPES OF MUTATION

F R A M E S H I F T, R E V E R S I O N A N D S P O N TA N E O U S

INTRODUCTION

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• Nucleic acids are the building blocks of DNA and RNA.• They carry the long-term memory of the information required for

an organism's reproduction.• Given the complexity of DNA and the vast number of cell divisions that take

place within the lifetime of a multicellular organism, copying errors are likely to occur.

• Mutation is the random process whereby genes change from one allelic form to another.

• Mutation can occur in two directions; mutation from wild type to mutant is called a forward mutation, and mutation from mutant to wild type is called a back mutation or reversion.

• In this presentation we are going to see in detail about three of such mutation that occur i.e. Frame-shift, Reversion and Spontaneous.

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FRAMESHIFT MUTATION

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• A frameshift mutation is a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read.

• The normal sequence of codons is disrupted by the insertion or deletion of one or more nucleotides, provided that the number of nucleotides added or removed is not a multiple of three.

• Frameshift mutations result in abnormal protein products with an incorrect amino acid sequence that can be either longer or shorter than the normal protein.

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REVERSION MUTAT ION

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• Reverse mutation (reversion) is the production by further mutation of a permutated gene from a mutant gene.

• Reversion is the correction of a mutation, i.e. it occurs at the same site; more loosely, though, the term is applied also to a mutation at another site that masks or suppresses the effect of the first mutation.

• In fact, such organisms are not non-mutant, but are double mutants with the same phenotype.

• Two types:- 1. True reversion is the reversal of the original nucleotide change. 2. Phenotypic reversion can result from changes that restore a different

amino acid with properties identical to the original. Second-site changes within a protein can also restore normal function.

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SPONTANEOUS MUTATION

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• Spontaneous mutations arise from a variety of sources, including errors in DNA replication, spontaneous lesions, and transposable genetic elements.

• These are mutations that are a result of natural changes in DNA structure.• All types of point mutations can occur spontaneously, during S, G1 and G2

phases of the cell cycle, or by the movement of transposons.• The spontaneous mutation rate in eukaryotes is between 10-4-to-10-6 per

gene per generation, and in bacteria and phages 10-5-to-10-7/gene/generation.

• Genetic constitution of the organism affects its mutation rate. • Spontaneous mutations Caused mainly by Spontaneous replication errors:- 1. Tautomeric shifts 2. Wobble base pairing 3.Strand slippage 4.Unequal crossing over 5.Spontaneous Chemical Changes i. Depurination ii. Deamination

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REFERENCE

• http://www.slideshare.net/sreerajsree/spontaneous-and-induced-mutations• http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/possiblemutations• https://youtu.be/eDbK0cxKKsk• http://

study.com/academy/lesson/mutagens-and-the-effects-of-frameshift-mutations-definitions-and-examples.html

• http://www.ncbi.nlm.nih.gov/books/NBK21897/• https://www.ndsu.edu/pubweb/~mcclean/plsc431/mutation/mutation3.htm• http://www.nature.com/scitable/topicpage/genetic-mutation-1127• http://medical-dictionary.thefreedictionary.com/reverse+mutation

THANK YOU

Dvane Coutinhodvanecoutinho@ymail.com