GENE MUTATION & ITS TYPES

Presented by: CS KAZIPYO15MSCGPB001 III SemesterM.Sc (Ag) Genetics & Plant Breeding

HOW DO MUTATION HOW DO MUTATION OCCUROCCUR

• Mutations may be natural or induced and may be occur at chromosome level or at gene or molecular level

• Spontaneous mutation is due to natural causes like errors in DNA application.

• Induced mutation is caused by artificial agents called mutagens (Physical radiation or Chemical compound).

TYPES OF GENE MUTATION

Point Mutation Substitution Insertion Deletion Frameshift

Point Mutation

• Missense Mutation: DNA → RNA → Protein (Change) (Change) (Change)

• Same/Silent Mutation: DNA → RNA → Protein (Change) (Change) (No Change)

• Non-Sense Mutation: DNA → RNA → Protein (Change) (Change) ( Stop)

• Missense Mutation:Change in nucleotide sequence brings different types of protein.

• Same/Silent Mutation:Change in nucleotide sequence brings no change in protein type. It is due to degeneracy of genetic.

• Non-Sense Mutation:Change in nucleotide sequence brings non-sense codon (UAA, UAG, UGA) at a new position in the mRNA as a result, protein synthesis adversely stops.

2. Base Substitution• Replacement of one base pair by another pair

in the DNA is known as base substitution.i) Transition:

Purine Purine Purine Purine

→ or →

→ or → Pyrimidine Pyrimidine Pyrimidine Pyrimidine

A

C

G

T

G A

CT

• ii) Transversion: Purine Pyrimidine Pyrimidine Purine

→ or →

→ or →

Pyrimidine Purine Purine Pyrimidine

A

T

T

C

G

G

C

A

3. Insertion

• Insertions are mutations in which extra base pairs are inserted into a new place in the DNA.

4. Deletion

• Deletions are mutations in which a section of DNA is lost, or deleted.

• If it occurs in coding sequences and involves one, two or more nucleotides which are not a multiple of three, it will disrupt the reading frame.

5. Frameshift Mutation•  Mutation caused by the addition or deletion of a

base pair or base pairs in the DNA of a gene resulting in the translation of the genetic code in an unnatural reading frame from the position of the mutation to the end of the gene