Board Thread:Theories and Speculation/@comment-26894845-20151212061943/@comment-1512913-20151212134718

I would say chakra works very similar to genes. The Uchiha may have Indra's Sharingan chakra/genes, but i'm sure there is much more to Indra's chakra than his eyes, they are just fragment of it. His descendants' chakras are similar, not the same, needs to be the same or at least "the Rinnegan" parts of Hagoromo's chakra/genes must be all present. Kinda like a puzzle.

Think of this as Indra's chakra: abcdefghij (abcde equals Indra's eyes, his Sharingan/half of Rinnegan) Think of this as Asura's chakra: 1234567890 (12345 equals whatever special power and the other half needed for the Rinnegan)

So lets say Izuna might have had Indra's abcd, but missed the e, so even if he were to get 12345, it wouldn't recreate the Rinnegan. Lets say Tobirama might have had Asura's 1234, but missed the 5, so even if he were to get abcde, it wouldn't recreate the Rinnegan. Or even if Izuna/Tobirama had had abcde/12345 (an entire Indra/Asura half of the Rinnegan), if he were to have gotten just 1234/abcd, nothing would have happened.