Sex determination in humans is a system which helps us to decide the sexual characteristics of the offspring. It also helps in determining the sex of the organism, whether the organism will be male or a female. The widely used technique for sex determination in humans is the chromosomal sex determination. In placental mammals, the presence of the Y chromosome determines the sex of the offspring. Normally, cells from the female parent contain two X chromosomes, and that from the male parent contains an X and a Y chromosome. Hence, we can say that the sex of the child is determined by the male gamete provided by the father. During spermatogenesis in males, both types of haploid gametes are produced, i.e., one carrying the X chromosome and one carrying the Y chromosome. At the time of fertilization, the sex of the resulting zygote will depend on which of the two sperms fertilizes the X of the mother. Hence, there is a 50% chance that the child will be a male and 50% that it can be a female.