Somatic cells in human beings contain 23 pairs of chromosomes. Out of them the 23rd pair is composed of X and Y chromosomes. In males, the 23rd pair contains one X and one Y chromosome. On the other hand, in a female the 23rd pair only contains X chromosomes. This means that the eggs would have X chromosome as the 23rd chromosome, while a sperm may have either X or Y chromosome as the 23rd chromosome. When a sperm with X chromosome fertilizes the egg, female child would be developed by the formed zygote. When a sperm with Y chromosome fertilizes the egg, the resulting zygote would develop into a male child.Thus, there are 50 – 50 chances of a male or female child and none of the parents may by responsible for the Sex determination in humans.