Um the X chromosome in a women comes from the mother and the paternal grandmother and grandfather because there is crossover between X and Y chromosomes (albeit

Um the X chromosome in a women comes from the mother and the paternal grandmother and grandfather because there is crossover between X and Y chromosomes (albeit very little). There's no need to worry about the Y chromosome disappearing because it's remarkably stable. This makes sense -- males with Y mutations die out and men are extremely good at producing offspring. This only good Y chromosomes are passed on. Nevertheless, the genes on the Y chromosome are like any other and if the Y chromosome were to disappear, natural selection would still push for a 50/50 sex ratio. The Y chromosome itself isn't necessary to make a male -- its genes can be spliced onto the X chromosome and function properly. Thus, if we saw loss of Y, we would likely see a 50/50 gender split but now based on presence of the SRY gene.