Board Thread:Naruto Discussions/@comment-3279282-20140413164418/@comment-28861328-20140413172355

Chakra has been stated over and over again to also be associated with someone's DNA. For example how Asura's chakra was in Hashirama's DNA and that, when put together with Madara's, the Rinnegan manifested. Or how Kabuto has Orochimaru's chakra inside of him because he has Orochimaru's DNA. Chakra and genes are very heavily connected.