Yes, Manx is genetic but that's not a manx. If he has a stump, mom bit it off.

Your hairless look very unhealthy and one looks to have megacolon(see the discoloring and bloating on the left side of the belly?) Notice how bony they look, but bloated. Could have parasites or megacolon.

It would be best to stay away from high white rats altogether since they have a greater risk for carrying and passing megacolon in their genes. It's a very painful way to die for the babies and they cannot be used as feeders. High white rats are just like your little stumpy tailed guy. Anything other than a self, hooded, berkshire, irish, english, will be considered high white. Head spots are even considered high white. www.ratguide.com