Board Thread:Naruto Discussions/@comment-945885-20140709082448/@comment-24593592-20140719194529

Skitts wrote: That seems to take biology backwards, that is, these mutations are passed on, but her descendants never have more than one of them.

Btw, it's established that Indra inherited the eyes of the Sage while Asura inherited his body. So yeah...real world biology doesn't apply here.