On the basis of possibilities of combination of the X,Y chromosomes, what percentage probability does a couple have having a son or a daughter? Show the same by making a cross.

The sex of a baby is determined by the type of male gamete that fuses with the female gamete.

All human beings have 23 pairs of chromosomes in their nuclei. Out of these 23 pairs, the last pair is known as the sex chromosome.

The human males have 23 pairs of chromosomes including XY sex chromosomes. Therefore, the male gamete has 22 chromosomes and either an X or Y sex chromosome.

Male gametes can be of two types: 22+X or 22+Y

Females have 23 pairs of chromosomes including XX sex chromosomes. Therefore, their gametes can only have 22 chromosomes and one X sex chromosome.

Type of female gametes: 22+X

Thus, as the mother provides only X chromosome, the sex of the baby is determined by the type of male gamete (X or Y) that fuses with the X chromosome of the female. Thus, there are 50 percent chances of having either male or female child.