A
genetic marker is a gene or
DNA sequence with a known location on a
chromosome that can be used to identify individuals or
species. It can be described as a variation (which may arise due to mutation or alteration in the genomic loci) that can be observed. A genetic marker may be a short DNA sequence, such as a sequence surrounding a single base-pair change (
single nucleotide polymorphism, SNP), or a long one, like
minisatellites.