Question

short note on DNA repair mechanism

Answer 1

In this article we will discuss about the definition and mechanisms of DNA repair.

Definition of DNA Repair:

One of the main objectives of biological system is to maintain base sequences of DNA from one generation to the other. Changes in DNA sequence arise during replication of DNA damage by chemical mutagens and radiation. During replication if incorrect nucleotides have been added, they are corrected through editing system by DNA Pol I and DNA Pol III.

The other systems also exist for correcting the errors missed by editing function. It is called mismatch repair system. Mismatch repair system edits the errors left by DNA Pol I and DNA III and removes the wrong nucleotides. Proof reading by Pol I and III.

DNA is always damaged and mutated by several chemicals and radiation. Only a few errors accumulate in DNA sequence. The stable errors cause mutation and the rest are eliminated. If errors in DNA sequence are corrected before cell division, no mutation occurs. However, there are some DNA damages which cannot be mutated because the damages are not replicated. Therefore, such damages cause cell death.

There are several types of damages that occur in DNA:

(a) Modification of one or more bases by highly reactive chemicals such as alkylating agents like nitroso-amine and nitrosoguanidine,

(b) Loss of purine bases due to local pH change,

Answer 2

there are three major DNA repairing mechanism
base excision
nucleotide excision and mismatch repair