Write notes on : Sex determination in the unborn baby.

Explanation

Sex determination in the unborn baby: All human beings have 23 pairs of chromosomes in the nuclei of their cells. Two chromosomes out of these are the sex chromosomes, named X and Y. A female has two X chromosomes while a male has one X and one Y chromosome. The unfertilised egg always has one X chromosome. But, testes produce two kinds of sperms. One kind has an X chromosome and the other kind has a Y chromosome. When a sperm containing X chromosome fertilises the egg, the zygote would have two X chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilisation, the zygote would develop into a male child.
This is how sex determination in the unborn baby occurs.