Board Thread:Naruto Discussions/@comment-945885-20140709082448/@comment-24593592-20140715032213

Yamato and Danzo didn't get wood release from Hashirama's chakra, but his corpse which should have been dry of chakra by that time. It was pure genetics.

Madara had got the Rinnegan because Hagoromo himself was manifesting inside of him. As shown in chapter 683. So it's similar to a tailed beast inside its jinchuuriki.