A<unk>  is a known DNA sequence. It can be described as a variation, which may arise due to mutation or alteration in the genomic loci, that can be observed. A<unk>  may be a short DNA sequence, such as a sequence surrounding a single base-pair change (single nucleotide polymorphism), or a long one, like microsatellites.
Genetic marker
Biomarker
Nanosensor
Pharmacogenetics
Diagnostic test
CHADS2 score
Spectroscopy
Selectable marker