why did female have x cromosomes only
Answers
In the XY sex-determination system, the female-provided ovum contributes an X chromosome and the male-provided sperm contributes either an X chromosome or a Y chromosome, resulting in female (XX) or male (XY) offspring, respectively. Hormone levels in the male parent affect the sex ratio of sperm in humans.
THEre are two types of sex chromosomes, one is called x chromosome and other is called Y chromosome.
A male has x and Y chromosomes. And a female has two x chromosomes . It means all the female gametes called ova will have only x chromosome.
If a sperm carrying x chromosome fertilieses an ovum which carries x chromosome , then the child will born a girl
And if a sperm carrying Y chromosome fertilises an ovum which carries x , then the child born will be a boy.