x2 to the bolded. I had a male Rex dumbo who was an odd-eye. He had a few babies in each litter he fathered with several different females that ended up with megacolon. It wasn't the girls, as they never threw any babies with any issues when I used different males, soooooooo...something to keep in mind but if you don't have any issues, I wouldn't worry about it. Mine were several generations in that it developed as an issue and he was older so who knows. Cute ratties, regardless.