Sex Determination in Man

A person’s sex is an inherited characteristic. There are 23 pairs of chromosomes in each body cell. Of these, one pair is directly concerned with sex determination and are called sex chromosomes, the other 22 pairs are known as autosomes. Autosomes are numbered roughly in relation to their sizes.

In males, the two sex chromosomes are not alike in shape and size. They are called X and Y chromosomes. 

Each male gamete carries either an X chromosome or a Y chromosome.

In human females, all the cells of the body contain two X- chromosomes. All eggs contain one X chromosome each.

When a sperm carrying either an X or Y chromosome combines with an egg the chances are equal. If a sperm with a Y chromosome combines with an egg, it forms a male baby (XY) but if the sperm with an X chromosome combines with an egg it will form a female baby with 2X chromosomes. 

What is the Probability of having a Boy or Girl?

	Female egg cells >	X	X
Sperm cells >	X	XX	XX	50%
	Y	XY	XY	50%