Describe the process of sex determination in humans.

Explanation

The sex determining mechanism in case of human is XX : XY type.
= In humans out of 23 pairs of chromosomes present 22 pairs are exactly same in both males and females known as autosomes.
= The `23^(rd)` pair of chromosome is the sex chromosome i.e. a pair of X-chromosome [XX] is present in females and males having one .X. and one .Y. chromosome [XY].
= During spermatogenesis, in case of males, two types of gametes are produced.
= The 50% of total sperms produced carry-chromosomes and the rest 50% carry Y-chromosomes besides autosomes.
= This condition is called male digamy.
= The Y-containing sperms and X-containing sperms are called andosperms and gynosperms respectively.
= Female produces only one type of ovum with an X-chromosome.
= If an ovum fertilises with a sperm carrying X-chromosome, the zygote develops into a female (XX) and if an ovum is fertilised with sperm carrying Y-chromosome zygote thus formed will be a male (XY).
= Hence the genetic make up of sperm, which fertilises the ovum determines the sex of a child.
= There are 50% chances of having either a male or female in each pregnancy.
= Thus it is a by chance phenomenon. So women should not be blamed for giving birth to a girl child.