Topic 8—A: Mutations and Gene expression-2. Mutagenic agents

Question 1

What are mutagenic agents?

Answer 1

They increase the rate of mutations

Question 2

Examples of mutagenic agents

Answer 2

• ultraviolet radiation
• ionising radiation
• some chemicals
• some viruses

Question 3

How can mutagenic agents increase the rate of mutations?

Answer 3

• acting as a base
• altering bases
• changing the structure of DNA

Question 4

Acting as a base

Answer 4

• chemicals called base analogs can substitute for a base during DNA replication
• This changes the base sequence in the new DNA
  E.g. 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

Question 5

Altering bases

Answer 5

• some chemicals can delete or alter bases
  E.g. Alkylating agents can add an alkyl group to guanine, which changes the structure so that it pairs with thymine (instead of cytosine)

Question 6

Changing the structure of DNA

Answer 6

• some types of radiation can change the structure of DNA, which causes problems during DNA replication
  E.g. UV radiation can cause adjacent thymine bases to pair up together