Question

Explain sex determination in an unborn baby. [3 MARKS]

Answer 1

Each point: 1 Mark

1. The sex of a baby is determined by the type of male gamete that fuses with the female gamete. All human beings have 23 pairs of chromosomes in their nuclei. Out of these 23 pairs, the last pair is known as the sex chromosome.

2. The human males have XY sex chromosomes. Females have XX sex chromosomes.

3. The sex of the baby is determined by the sex chromosome that is contributed by the male, either X or Y. Females have XX chromosome hence they always contribute an X chromosome.
If the male contributes an X chromosome then the baby is girl and if Y, then boy.