The sex chromosome present in males of species in which the male is the heterogametic sex; generally, the sex chromosome that pairs with the X chromosome in the heterogametic sex. The Y chromosome is absent from the cells of females and present in one copy in the somatic cells of males.
Source:ISBN:0582227089,
Wikipedia:XY_sex-determination_system,
PMID:20622855,
GOC:mah,
GOC:mr