Mutation: causes, types, rates, and evolution

Definition and scope of mutation

A mutation is an alteration in the nucleotide sequence of an organism’s genome (including viruses and extrachromosomal DNA). It can arise from errors during DNA replication or cell division (mitosis/meiosis), or from DNA damage that leads to error-prone repair or replication (such as translesion synthesis). Mutations may also occur through structural changes caused by mobile genetic elements, including substitutions, insertions, and deletions. Mutations may or may not produce observable changes in phenotype. Their scope includes effects in both genic and non-genic regions: mutations in genes can have no effect, change gene products, or disrupt gene function, while mutations outside genes can also contribute to genetic variation. At the cellular level, mutations can alter protein function and regulation; at the population level, the frequency of mutations changes according to their impact on survival and reproduction, thereby influencing evolution, cancer development, and immune system diversity. Overall, mutations are distinct from DNA damage: DNA damage is a physical alteration that can block transcription/replication and may be repaired using templates, whereas mutations are sequence changes that are replicated along with the cell’s DNA and are not typically “recognized” for repair once both DNA strands carry the altered base. Because mutations are the ultimate source of genetic variation, they provide the raw material on which evolutionary forces act.

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Phenotypic effects and detectability

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