Question

In human beings, the sex of the child is determined by the father and not by the mother. Explain.

Answer 1

In human beings, the sex of the child is determined by the father and not by the mother because of the difference in the sex chromosomes contributed by each parent. Females have two X chromosomes (XX), so they can produce only one type of gamete (egg), each carrying an X chromosome. Males have one X and one Y chromosome (XY) and produce two types of gametes (sperms): half carry an X chromosome and half carry a Y chromosome.

During fertilization, the sperm determines the sex of the child by which chromosome it carries and fuses with the X chromosome of the egg:

• If a sperm carrying an X chromosome fertilizes the egg (X), the resulting zygote will have XX chromosomes, producing a female child.
• If a sperm carrying a Y chromosome fertilizes the egg (X), the resulting zygote will have XY chromosomes, producing a male child.

Therefore, since the mother always contributes an X chromosome, the variability of the sex of the offspring depends on whether the father contributes an X or a Y chromosome through his sperm. This is why the father, not the mother, determines the sex of the child.

Consequently, it is scientifically incorrect to blame the mother for the sex of the child, as the determining factor lies in the father's contribution of either the X or Y chromosome.