Human follows XX- XY mechanism of sex determination in which females have forty-six chromosomes arranged in twenty-three homologous, homomorphic pairs. Males have twenty-two homomorphic pairs and one heteromorphic pair, the XY pair. During meiosis, all the gametes produced by females contain only the X chromosome (22 A + X), whereas males produce two kinds of gametes, 1/2 gametes with X- and 1/2 with Y-chromosome (22 A + X and 22 A + Y). Fertilization of egg (22 + X) with sperm carrying 22+X chromosomes results in female child (44A + XX). Fertilization of egg (22 + X) with a sperm carrying 22+Y chromosomes results in a male child (44A + XY).