Genetic markers are genes or DNA sequences with a known location on a chromosome used to identify individuals or taxa. The use and identification of genetic markers is based on the variation of loci that arise due to mutation and recombination errors.
Geneti markers may be as short as a single nucleotide polymorphism (SNP) or as long as a minisatellite, which involve several-base-long alleles organized in a series of tandem repeats.
There are two categories for genetic markers: Co-dominant and dominant. Co-dominant markers include microsatellites, minsatellites, SNPs and RFLPs, and are used to analyze a single locus with known allelic characteristics. Dominant markers include AFLPs, RAPDs and SMPLs, and are used to analyze multiple loci with unknown allelic characteristics (also known as profiling).