Mutation

Changes to DNA are called mutations. If mutations affect genes involved in controlling the cell cycle, normal checks on division can fail. Mutations can occur by chance when cells divide or can be made more likely by damaging agents.

Cancer results from changes in cells that disrupt these normal controls. These changes can include mutations in DNA. If genes involved in controlling the cell cycle are altered, a cell may no longer respond properly to signals that tell it when to divide or stop dividing.

A mutation changes that sequence. The changed version is a genetic variant: all genetic variants ultimately arise from mutations. Mutations can occur by chance when DNA is copied, and factors such as ionising radiation can also cause them.

A mutation is a change in the nucleotide base sequence of DNA. It is an event: the sequence that was present before the mutation becomes a different sequence afterwards.