DNA mutations and repair

How do DNA mutations arise?

Mistakes during DNA replication, damage from environmental agents, spontaneous hydrolytic reactions (aging)

2 examples of damaging environmental agents and what effect they have

Nitrous acid (C→U) and UV light (link 2 neighbour Ts together)

What is an intercalating agent and what does it do?

A planar molecule that can insert itself between two adjacent base pairs, leading to the addition of an extra base on the opposite strand during replication (DNA polymerase picks a base at random). It leads to a frameshift mutation

Example of an intercalating agent

ethidium bromide

What is depurination?

Separation of a base and the backbone, without the breaking of the phosphodiester bond

What is the result of spontaneous hydrolytic reactions?

Depurination, deletion of a base pair in one of the molecules after replication