A2. Mutagenic Agents

Question 1

What are mutagenic agents?
Mutations occur spontaneously, e.g. when DNA is misread during replication. But some things can increase the ____ of ____________- these are called mutagenic agents. Ultraviolet radiation, ionising radiation, some chemicals and some viruses are examples of mutagenic agents. They can increase the rate of mutations in different ways. (3 ways with description and example)

Answer 1

What are mutagenic agents?
Mutations occur spontaneously, e.g. when DNA is misread during replication. But some things can increase the rate of mutations - these are called mutagenic agents. Ultraviolet radiation, ionising radiation, some chemicals and some viruses are examples of mutagenic agents. They can increase the rate of mutations in different ways.

1. Acting as a base
   Chemicals called base analogs can substitute for a base during DNA replication, changing the base sequence in the new DNA.

Example
5-bromouracil is a base analog that can substitute for thymine. It can pair with guanine (instead of adenine), causing a substitution mutation in the new DNA.

2. Altering bases
   Some chemicals can delete or alter bases.

Example
Alkylating agents can add an alkyl group to guanine, which changes the structure so that it pairs with thymine (instead of cytosine).

3. Changing the structure of DNA
   Some types of radiation can change the structure of DNA, which causes
   problems during DNA replication.

Example
UV radiation can cause adjacent thymine bases to pair up together.