DNA Mutation and Genotoxicity

DNA Mutation and Damage

• A mutation is a change in a base pair, such as from a G-C pair to an A-T pair, which is a permanent alteration in the DNA sequence.
• DNA damage, on the other hand, is a chemical alteration to DNA that can be repaired, such as the change from a G-C pair to an ethyl-G-C pair.
• Genotoxic DNA damage is likely to lead to a mutation, and an example of this is the ethyl-G damage that can mispair with T instead of C during DNA replication.

Conversion of DNA Damage to Mutation

• The conversion of DNA damage to a mutation requires DNA replication, as illustrated in the example of ethyl-G damage.
• In this example, the ethyl-G damage can lead to the mispairing of T with ethyl-G, resulting in the conversion of a normal G-C pair to an A-T pair (a true mutation).

Types of DNA Damage

• Two common examples of DNA damage are:
  • Base modifications caused by alkylating agents
  • Pyrimidine dimers caused by ultraviolet radiation

Cellular Response to DNA Damage

• Bacterial and eukaryotic cells have mechanisms to deal with DNA damage, most of which involve DNA replication.
• These mechanisms are important for repairing DNA damage and preventing mutations.