DYS is short for DNA Y-chromosome Segment, and is used to designate a segment of DNA on the Y chromosome where a sequence of nucleotides repeats. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known The Y chromosome is the sex-determining Chromosome in most Mammals including Humans In mammals it contains the gene SRY, which triggers Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group These sequences are known as short tandem repeats (STRs), and are called markers in genealogical DNA testing. A short tandem repeat (STR in DNA is a class of polymorphisms that occurs when a pattern of two or more Nucleotides are repeated and the repeated sequences A genealogical DNA test examines the Nucleotides at specific locations on a person's DNA for Genetic genealogy purposes The possible variations of repeats at a DYS marker are known as alleles. An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms
Some testing companies have different formats for the way DYS markers are written, for example, the location 455 may be written as DYS455, DYS 455, DYS#455, or DYS# 455.