Which one of the following is true regarding sex determination in human beings?

During spermatogenesis among males, two types of gametes are produced. 50 percent of the total sperm produced carry the X-chromosome and the rest 50 percent have a Y-chromosome besides the autosomes. Females, however, produce only one type of ovum with an X-chromosome. In case the ovum fertilizes a sperm carrying X-chromosome, the zygote develops into a female (XX), and the fertilization of the ovum by a sperm carrying Y-chromosome results in male offspring (XY). Thus, it is evident that the genetic makeup of the sperm determines the sex of the child. The y chromosome has TDF(Testis Determining Factor) which determines the male sex. Its absence in zygotes leads to the female sex.

Barr's body represents inactivated X-chromosome. It is usually present in women but absent in men.