In a human being, sex of a child is determined depending upon which kind of male gamete fertilises with the female gamete. There are 23 pairs of chromosomes in each of the maternal and paternal copy. Out of 23 pairs,
22 pairs are said to be autosomes (A) and one pair is called sex chromosomes (in male XY and female XX). At the time of fertilisation, the egg cell fuses with the sperm cell to form the zygote. If the sperm carrying X chromosome fertilises an ovum carrying X chromosome, then the child born will be a girl. If the sperm carrying Y chromosome fertilises an ovum carrying X chromosome, the child born will be a boy.
