Write notes on Sex determination in the unborn baby.

Explanation

Sex determination in the unborn baby. Inside the fertilized egg or zygote is the instruction for determining the sex of the unborn. This instruction is present in the threadlike structures, called chromosomes in the fertilised egg. The chromosomes are present inside the nucleus of every cell. 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 gametes (egg and sperm) have only one set of chromosomes. 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 chromo-some to the egg (ovum) at fertilisation, the zygote would develop into a male child. (see Fig.)

Therefore the sex chromosomes of father determine the sex of an unborn baby.