Determining biological sex in offspring

In the process of reproduction, a male's sperm and a female's egg each contributes one sex chromosome.

A child's biological sex (male or female) is determined by the chromosome that the male parent contributes. Males have XY sex chromosomes while females have XX sex chromosomes; the male can contribute the X or Y chromosome, while the female must contribute one of their X chromosomes. A male infant results if the male contributes his Y chromosome while a female infant results if he contributes his X chromosome.