Sex determination seen in humans is XY sex determination. Ovum carries X chromosome, whereas sperm can carry either X or Y chromosome. The genetic makeup of a female is XX and genetic makeup of male is XY. Therefore, if the zygote is formed by receiving the X chromosome from the father, the resulting zygote will be a female.
During sexual intercourse, the father ejects both types of sperms, i.e. X chromosome and Y chromosome sperms.
- If the sperm with an X chromosome fertilizes the ovum of the X chromosome, the zygote would have XX chromosomes, and the child will be a girl.
- If the sperm with the Y chromosome fertilizes the ovum of the X chromosome, then the zygote would have XY chromosomes, and the child will be a boy.