GLOSSARY: Y Chromosome
A Y Chromosome is defined as a sex chromosome that is characteristic of male zygotes in species in which the male typically has two unlike sex chromosomes. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs. DNA in the Y chromosome is passed from father to son, thus tracking many surnames. Y-DNA analysis is thus used in family history research.