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?
A baby's biological sex is determined by the sex chromosomes inherited from the parents. Females have XX chromosomes, while males have XY chromosomes.
During reproduction, the mother always contributes an X chromosome to the baby. However, the father contributes either an X chromosome or a Y chromosome.
If the father contributes an X chromosome, the baby will be female (XX). If he contributes a Y chromosome, the baby will be male (XY). Therefore, the father determines the sex of the baby.
Explanation
The textbook context explicitly states that females have XX chromosomes and males have XY chromosomes. Since the mother always provides an X chromosome, the sex of the baby depends entirely on whether the father's sperm carries an X or a Y chromosome. Thus, the father determines the biological sex of the baby.