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

Sex-determination in humans:

1. The sex of a baby is determined by the type of male gamete that fuses with the female gamete.
   
2. All human beings have 23 pairs of chromosomes in their nuclei.
   
3. Out of these 23 pairs, the last pair is known as the sex chromosome.​
4. The sex chromosomes in human males is XY and hence the gamete produced by them will have either X chromosome or Y chromosome.
5. Females have XX chromosome hence they always contribute an X chromosome in their female gametes.
   
6. The sex of the baby is determined by the sex chromosome that is contributed by the male, either X or Y as the specific male gamete that fuses will define the sex of the baby.
7. If the male contributes an X chromosome then the baby is girl and if Y, then the baby will develop into a boy.