Question

What determines a baby’s biological sex? So far, you have learnt that every person has two sex chromosomes. Females have XX and males have XY chromosomes. The mother always contributes an X chromosome to a baby and the father contributes either an X (Female: XX) or a Y (Male: XY) chromosome. Now, from the above information, can you predict who determines the sex of a baby?

Answer 1

The father determines the biological sex of the baby. The mother always contributes an X chromosome, while the father contributes either an X or a Y chromosome: an X from the father gives a girl ($$\mathrm{XX}$$), and a Y from the father gives a boy ($$\mathrm{XY}$$).