The sex of a child in human beings in genetically determined. The humans have 23 pairs of chromosomes, out of which 22 are a perfect pair of one paternal and one maternal copy. The last pair of chromosomes also called the sex chromosomes, is different for males and females. Females have a pair of X chromosomes, whereas males have XY chromosomal pair. The inheritance of these sex chromosomes that determine the gender of an individual is as follows :