11. How is sex determined in human beings?
Sex determination in human beings
In humans, out of 23 pairs of chromosomes, 22 pairs are exactly the same in male and female called autosomes. However, a pair of the X chromosome is present in female and XY in male. During spermatogenesis, male produce two types of gametes (sperms), 50% carries Y chromosome and remaining 50% contain X chromosome. On the other hand, female produces only one kind of gamete (ovum) having X chromosomes only. When sperm having Y chromosome fertilises the ovum the sex of the baby is male and when sperm carrying X chromosome fertilises the egg, the sex of the baby is female.