Sex of the human baby is determined based on the type of

During spermatogenesis two types of gametes are produced by males. 50 per cent of the total sperm produced carrythe X-chromosome and the rest 50 per cent has Y-chromosome besides the autosomes. Females produce only one type of ovum with an X-chromosome. There is an equal probability of fertilisation of the ovum with the sperm carrying either X or Y chromosome. Thus, it is evident that it is the genetic makeup of the sperm that determines the sex of the child.