MP Board · Class 10 · Science · Heredity and EvolutionExplain how sex determination is genetically regulated in human beings.

Sex determination in human beings is a genetic process determined by the type of sex chromosomes inherited from the parents at the time of fertilization. Human beings possess 23 pairs of chromosomes, out of which 22 pairs are autosomes and one pair consists of sex chromosomes. Females have two identical sex chromosomes designated as XX, while males have a mismatched pair consisting of one large X chromosome and one smaller Y chromosome designated as XY. During gamete formation, females produce eggs that all carry a single X chromosome (22 + X). In contrast, males produce two different types of sperms in equal proportions: half the sperms carry an X chromosome (22 + X) and the other half carry a Y chromosome (22 + Y). When a sperm carrying an X chromosome fertilizes an egg with an X chromosome, the resulting zygote will have XX chromosomes and develop into a female child. If a sperm carrying a Y chromosome fertilizes an egg with an X chromosome, the resulting zygote will have XY chromosomes and develop into a male child. Therefore, scientifically, the father's contribution of either an X or a Y chromosome is solely responsible for determining the sex of the child.