Mutations

You must have heard about mutations right??

Mutation are basically the permanent changes that occur In the DNA sequence.

The agents that cause these mutations are called mutagens.

( Not the one that turned Wolverine into .... Wolverine..!!)

(.. yeah bad sense of humor..haha 😅).

..

Mutations in germ cells are transmitted to the next progeny and may give rise to inherited diseases.

But the somatic cell mutations are not transmitted but , are important causation of cancers and congenital malfunctions.

Causes of mutation:

1. Error in replication

2. Error due to recombination events.

3. Spontaneous change in DNA

4. Environmental factors like irradiation.

Now, let's talk about types of mutations.

I'll provide with the flowchart here,

(The above image is from my textbook.)

1. Point mutations: only one base in DNA is altered.

It's subtypes are:

• Silent : there is no detectable change even after the mutation.

Eg: codon change from CGA to CGG doesn't affect the protein because both specify for arginine.

• Missense : different amino acid is incorporated at the corresponding site in protein molecule.

Eg: aspargine substitute for lysine at the 61 position in B- chain of hemoglobin.

• Nonsense : conversion of an amino acid codon into a stop codon resulting in termination.

Eg: in one type of thalassemia, codon 17 of B-chain of hemoglobin is changed from UGG TO UGA.

2. Frame shift mutations: when there is insertion or deletion of one or more nucleotide in DNA.