Sex is determined in human beings

Options

A. By ovum
B. At time of fertilization
C. 40 days after fertilization
D. Seventh to eight week when genitals differentiate in foetus

Answer

B

Explanation

During spermatogenesis among males, two types of gametes are produced. 50 per cent of the total sperm produced carry the X-chromosome and the rest 50 percent has Y-chromosome besides the autosomes.
Females, however, produce only one type of ovum with an X-chromosome.
There is an equal probability of fertilisation of the ovum with the sperm carrying either X or Y chromosome.
In case the ovum fertilises with a sperm carrying X-chromosome the zygote develops into a female (XX) and the fertilisation of ovum with Y-chromosome carrying sperm results into a male offspring.
Thus, it is evident that it is the genetic makeup of the sperm that determines the sex of the child.
It is also evident that in each pregnancy there is always 50 per cent probability of either a male or a female child.