MP Board · Class 10 · Science · HeredityExplain how sex determination is genetically regulated in human beings with the help of a brief description.

Sex determination in human beings is a fascinating genetic process regulated by specific sex chromosomes inherited from the parents. Every human somatic cell typically contains 23 pairs of chromosomes, making a total of 46 chromosomes. Out of these 23 pairs, the first 22 pairs are known as autosomes, which determine general body characteristics and are identical in males and females. The 23rd pair consists of the sex chromosomes, which directly determine the biological sex of the individual. Females possess two identical large sex chromosomes designated as XX, which means all female gametes (eggs) carry a single X chromosome. On the other hand, males possess a mismatched pair of sex chromosomes designated as XY, where X is large and Y is remarkably smaller. Because of this XY constitution, human males produce two different types of sperm cells in equal proportions: 50% of the sperms carry an X chromosome, while the other 50% carry a Y chromosome. The biological sex of the child is entirely determined during fertilization by whichever sperm successfully fuses with the egg. If a sperm carrying an X chromosome fertilizes the egg (which always carries an X), the resulting zygote will have the XX combination, developing into a female child. Conversely, if a sperm carrying a Y chromosome fertilizes the egg, the zygote will have the XY combination, developing into a male child. Thus, scientifically, the father's sperm plays the decisive role in determining the sex of the child.