How is the sex of a newborn determined in humans?
Somatic cell of human beings has 23 pairs of chromosomes. Out of them the 23rd pair contains sex chromosomes. In a male, the somatic cell has X and Y chromosomes in 23rd pair. In female, the somatic cell has XX chromosomes in 23rd pair. So, a sperm can have either X or Y chromosome as the 23rd chromosome. On the other hand, an egg has X chromosome as the 23rd chromosome. When a sperm with X chromosome fertilizes the egg, the resulting zygote develops into a girl child. When a sperm with Y chromosome fertilizes the egg, the resulting zygote develops into a male child.
