mutation
Definition:
A mutation is any change in a gene passed from one generation to another. Most mutations are naturally occuring changes from parent to child.
Examples:
An alleged father may have an allele measuring '15' at a certain location but, when passed to a child, the allele may change slightly and become '15.2' or '16.' Paternity testing can determine whether these changes are a natural mutation or a non-match between an alleged father and child.
see also: allele, chromosome, gene, locus

