Mutagenic agents

• mutations occur spontaneously e.g. when DNA is misread during replication
• but some things can increase the rate of mutations - mutagenic agents
• • UV radiation
  • ionising radiation
  • some chemicals
  • some viruses
• DNA replicates itself everytime a cell divides
• mutagenic agents can increase the rate of mutations in different ways:

  • acting as a base
  • altering bases
  • changing the structure of DNA
• • acting as a base
  • chemicals called base analogs can substitute for a base during DNA replication, changing 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
• • altering bases
  • some chemicals can alter or delete bases
  • e.g. alkylating agents can add an alkyl group to guanine - changes the structure so that it pairs with thymine (instead of cytosine)
• • changing the structure of DNA
  • 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