Two type of gametes are formed in male, one type is having 50% X-chromosome, whereas, other type is having Y-chromosome. In female, gametes are of one type and contain X-chromosome. Thus females are homogametic. If male gamete having Y-chromosome (androsperm) undergoes fusion with female gamete having X-chromosome, the zygote will have XY chromosome and this gives rise to male child.

If male gamete having X-chromosome (gynosperm) undergoes fusion with female gamete having X-chromosome, the zygote will be having XX-chromosome and this gives rise to female child.

â–² Genetics of sex in human beings. The letter A represents autosomes.