a gene with a clear, unambiguous phenotype used in genetic analysis to identify individuals that carry it or other linked genes. May act as a probe to mark a nucleus, chromosome or locus. [CUB
A piece of DNA or a gene whose properties (and sometimes also their position on the chromosomes) are known and can be used to identify particular cells or organisms; they might also be used as a reference point in a genetic mapping experiment.
a DNA sequence used to "mark" or track a particular location (locus) on a particular chromosome