Also known as a genetic marker, a segment of DNA with an identifiable physical location on a chromosome whose inheritance can be followed. A marker can be a gene, or it can be some section of DNA with no known function. Because DNA segments that lie near each other on a chromosome tend to be inherited together, markers are often used as indirect ways of tracking the inheritance pattern of genes that have not yet been identified, but whose approximate locations are known.

Dr. Leslie Biesecker, of the National Human Genome Research Institute's Laboratory of Genetic Disease Research, defines marker.

Related terms: deoxyribonucleic acid (DNA), chromosome, gene, gene mapping, inherited.