Answer:
Because the offspring of a male and female are always going to be xx, xx, xy, or xy.
Explanation:
Remember that men have different reproductive chromesomes than women. Women have 2 x chromesomes(xx) while men have 1 x and 1 y(xy). These are given down to their offspring.
So we can write the this out in a punnet square as(link down below).
After you see the visual, you will find that the genotypes are xx, xx, xy, xy.
As I said above, women have sex chromesomes xx, while men have sex chromesomes xy. When you match the genotypes on the punnet square with the ones we know from men and women, we find that two of them match with men and two match with female.
So with this, we can conclude that 2/4 of offspring will always be male and 2 will be female. And as you well know 2/4 is 1/2 which is 50%.
