Chromosomes have DNA in them. They help to mainatain similarity between the parent and the offspring. Sex chromosomes help to determine the sex of a child. Each of the parent have 23 pairs of chromosomes out of which one is a sex chromosome. The father carries XY and the mother carries XX. If the male sperm carrying Y fuses with the female egg X , a male child will be born. If a male carrying X fuses with a frmale carrying X ,child born will be a girl.