The small chromosome that carries a dominant gene conferring maleness. Normal males have two matched chromosomes pairs and one unmatched pair, comprising one X-chromosome and one Y-chromosome. During production, the mother contributes an X-chromosome, but the father contributes an X or Y-chromosome. XX produce a female offspring and XY a male.
Y-Chromosome
chromosome that carries a dominant gene conferring maleness. Normal males have two matched chromosomes pairs and one unmatched pair, comprising one X-chromosome and one Y-chromosome. During 
production, the mother contributes an X-chromosome, but the father contributes an X or Y-chromosome. XX produce a female offspring and XY a male.