When male and female gametes fuse during fertilisation, sex is formed. Gametes with an X or Y chromosome are produced by males, whereas gametes with an X chromosome are produced by females. When male and female gametes combine to form a zygote during fertilisation, the sex of the baby is determined.
The offspring will be a girl if a sperm (male gamete) with an X chromosome fertilises an egg or an ovum (female gamete) with an X chromosome (female). This is due to the fact that the offspring will have XX sex chromosomal combinations.
The offspring will be a boy if a sperm (male gamete) with a Y chromosome fertilises an egg or ovum (female gamete) with an X chromosome (male). This is due to the fact that the offspring will have XY sex chromosome combinations.
Therefore, there is a 50% chance of a male child and a 50% chance of a female child.
