1. Each human cell contains 23 pairs (46) of chromosomes.
2. Out of 23 pairs, 22 pairs of chromosomes are called autosomes.
3. Remaining one pair is called allosomes or sex chromosomes.
4. There are two types of sex chromosomes – one is ‘X’ and the other is ‘Y’.
5. These two chromosomes determine the sex of an individual.
6. Females have two ‘X’ chromosomes in their cells (XX).
7. Males have one ‘X’ and one ‘Y’ chromosomes in their cells (XY).
8. All the gametes produced by women (ovum) will be with only X chromosomes.
9. The gametes produced by man (sperm) will be of two types, one with X chromosomes and other with Y chromosomes.
10. If the sperm carries X chromosome and fertilizes with the ovum, the resultant baby will have XX condition. So the baby will be a girl.
11. If the sperm carries Y chromosome and fertilises with the ovum, the resultant baby will have XY condition. So the baby will be a boy.
