Question

Explain the following.

How the sex of a child depends upon its father.

Answer 1

1. In human beings, the mother has XX sex chromosomes, so all ova (eggs) carry only the X chromosome.
2. The father has XY sex chromosomes and produces two types of sperms, 50% carry the X chromosome and 50% carry the Y chromosome.
3. If an X-bearing sperm fertilises the ovum (X), the zygote will be XX, and a female child is born.
4. If a Y-bearing sperm fertilises the ovum (X), the zygote will be XY, and a male child is born.

Therefore, the sex of the child depends upon the type of sperm contributed by the father, giving an equal 50% chance of a boy or a girl.