Inheritance of sex
Gender determinationHuman body cells have 23 pairs of chromosomes in the nucleus. One of these pairs controls the inheritance of gender - whether offspring are male or female:
- In males, the two sex chromosomes are different. They are XY
- In females, the two sex chromosomes are the same. They are XX
Gametes (sperm and eggs) are made through a special type of cell division called Meiosis (May-o-sis). This results in cells with half a set of DNA. The male has a pair a chromosomes X and Y. When his sperm are made half receive the X and half receive the Y.
I females all the chromosomes are X, so the eggs must all be X too.
The diagram demonstrates that if we look at the different possible matches between sperm and eggs, the chance that the offspring being male is equal to the chance of being female.
I females all the chromosomes are X, so the eggs must all be X too.
The diagram demonstrates that if we look at the different possible matches between sperm and eggs, the chance that the offspring being male is equal to the chance of being female.