A spontaneous change in the genetic composition of an organism at the gene, chromosome, or genomic level. Mutations usually refer to alterations to new allelic forms, and represent new material for evolutionary change.

In genetics, a permanent, heritable change in the nucleotide sequence of a chromosome, usually in a single gene; commonly leads to a change in or loss of the normal function of the gene product.

are the changes of a gene from one allelic form to another (i.e., the nucleotide sequence changes).

a change in the genetic material (DNA) of a cell, or the change this causes in a characteristic of the individual, which is not caused by normal genetic processes.