Why are there not more females than males if chromosome pairs split into gametes to be paired up again?

Question

This might not make much sense but I just read that gametes come from XX splitting to X and X and the same for XY into and X and a Y. Assuming these are evenly occurring then there are 75% X and only 25% Y, surely there’s more chance for XX pairs than XY occurring?

In: Biology

Answer 1

The ovum is always X. The sperm are 50/50 X or Y. It’s the sperm that’s the deciding factor, hence 50/50 male to female result.