Horses and Donkeys have differing numbers of chromosomes and yet (extremely rarely) produce fertile mules. In a more common case, women with down's syndrome hav

Horses and Donkeys have differing numbers of chromosomes and yet (extremely rarely) produce fertile mules. In a more common case, women with down's syndrome have an extra chromosome and yet are sometimes fertile. I understand that this is extremely common with plants, but that's pretty far outside my wheelhouse. I don't think we're disagreeing here, just simplifying like all conversations about biology.