Board Thread:Naruto Discussions/@comment-25442710-20140920121351/@comment-24653630-20140922163523

From Naruto Answers...

"You are correct. Hagoromo said that the Rinnegan is caused by having both the chakra of Indra and Asura, the Sharingan has nothing to do with it. Some people feel that the Rinnegan is an advanced form of the Eternal Mangekyo Sharingan, but it is not. This is caused by Kabuto's assumption that the Sharingan becomes the Rinnegan, which is not the case. The Rinnegan and Sharingan are two entirely different dojutsu. Madara needed to activate one or the other to use it, and he needed to switch back to Sharingan to use genjutsu.

However, Sasuke is using a combination of Rinnegan and Sharingan. His Rinnegan is different, as he uses the Rinnegan of the Ten-Tails, a Rinnegan/Sharingan duo. This Rinnegan as the power to use Genjutsu: Sharingan and Amaterasu.

If Naruto transplanted Sasuke's DNA, he'd get Indra's Chakra and the Rinnegan. It's that simple.

Black Zetsu said that he tried to get both the descendants of Indra AND Asura to activate the Rinnegan. The Uchiha were just more prone to temptation because they valued power more. Madara was just another example."