A sequence-tagged site (or STS) is a short (200 to 500 base pair) DNA sequence that has a single occurrence in the genome and whose location and base sequence are known.
[1] STSs can be easily detected by the polymerase chain reaction (PCR) using specific primers.
For this reason they are useful for constructing genetic and physical maps from sequence data reported from many different laboratories.
They serve as landmarks on the developing physical map of a genome.
For example, some STSs can be used in screening by PCR to detect microdeletions in Azoospermia (AZF) genes in infertile men.