How are horses and donkeys able to interbreed and produce a mule. Don't their genetypic variation or chromosomal difference prevent them from doing so? If not, then why not?
In closely related species chromosome has only some genetic variations. Therefore there is chance of their chromosomes joins. But if interbreed occurs the species will not be fertile. The ova of female species can take the most compatible from the closest male type .
It's not like that different species can't breed, in many cases they can. For example Donkey and horse , tiger and lion, etc, but the fact is that when different species breed they do not Produce fertile offsprings. Hinney, mules, liger and other animals that are produced by breeding between different species are infertile.