Mutation

A change in the nucleotide sequence in the DNA.

Mutations can result from errors during DNA replication or induced by exposure to mutagens (like chemicals and radiation), causing genetic dysfunction or creating new cellular functionalities. They can occur spontaneously or be inherited. Spontaneous mutations usually occur at a rate of 1 in 105 to 108 bacterial cells and contribute to random population variation.

Determinants of spontaneous mutation in the bacterium Escherichia coli as revealed by whole-genome sequencing (PNAS, 2015)