Board Thread:Theories and Speculation/@comment-26422608-20150522042352/@comment-734582-20150530121903

Raid998 wrote: Uchiha's power is in their dojutsu And Senju's is in their body

So, for an Uchiha, He must have a senju's DNA to awaken the rinnegan And for a Senju, he must only have the Sharingan to awaken it

That's what i think Considering that the Sharingan is apparently a reaction of an Uchiha's body, i would say that it's possible for Senju to obtain a "natural" sharingan. However, just like for Madara, it would probably require a lot of maturing to do before the Rinnegan is obtained. After all, Madara obtained the Rinnegan pretty much on his death bed.