Section: Science

97) The Smiths have four children, all girls. Their fifth child is a boy. Why did this change occur?

1. the conception classes taken by the parents.
2. the timing of the fertility cycles.
3. the mother's contribution of a Y chromosome.
4. the father's contribution of a Y chromosome.
5. the "law of averages" finally catching up.

The Y chromosome that determines a child's gender is carried by the father.