Brought it up in the "create a what if" thread, decided to risk giving it a seperate one. Mildly inspired by Alara Rogers' XXY Genderswap project, which was partially created to focus on mutants as feminists. Prepare for terrible genetic science!
So, what I'm proposing is that the X-gene only manifests itself when the carrier has two x-chromosomes. The carriers with xy chromosomes still have the X-gene, but it doesn't manifest itself, so the carrier doesn't have powers. In other words, the male mutants of canon still exist, they just don't have powers, though their daughters will.
What happens when there's no Professor X, Magneto, Apocalypse, or Cyclops, but there is Destiny, Mystique, Selene, and Jean Grey?