A variety of mechanisms that help to ensure that the genetic sequence, as expressed in the DNA, is maintained and that errors that occur during DNA replication, by mutation, are not allowed to accumulate. An error in the genetic sequence could cause cell death by interfering with the replication process. The mechanisms work because DNA is made up of two complementary strands. A damaged section of a strand, or a mismatched base, can be removed by enzymes and replaced by the correct form by DNA polymerases. The phosphodiester backbone is then sealed by DNA ligase. See excision repair; mismatch repair; postreplicative repair; proofreading.