Board Thread:Theories and Speculation/@comment-26422608-20150522042352/@comment-26155149-20150528163211

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