A certain man always complains that his wife can only bear female children. Your knowledge to explain to this man, using a cross diagram, that he is responsible for determining the sex of the children.

In humans, females have two X chromosomes (XX), and males have one X and one Y chromosome (XY).

• Parental Phenotypes: Male $\times$ Female
• Parental Genotypes: $XY \times XX$
• Gametes:
  • Male: X, Y
  • Female: X, X

The Punnett square illustrates the possible combinations of gametes from the parents.

From the Punnett square, the possible offspring genotypes are:

• XX (Female): 2 out of 4, or 50%
• XY (Male): 2 out of 4, or 50%

This means there is a 50% chance of having a female child and a 50% chance of having a male child with each pregnancy.

The sex of a child is determined by the father, not the mother. The mother always contributes an X chromosome to her offspring. The father, however, can contribute either an X chromosome (resulting in a female child, XX) or a Y chromosome (resulting in a male child, XY). Therefore, the man's complaint is incorrect, as he is the one who determines the sex of his children, and there is an equal probability of having a son or a daughter in each pregnancy.