Loophole!

[The God of Wind]

according to the manga izanami was created to reform izanagi users, we know from the manga that you need senju cells to use izanagi with the sharingan. how would all the izanagi users from the old uchiha clan get their hands on these cells? this is a blunder.

 

[abhiraj]

TOBI said that u need senju cells. and we all know that he is a liar

 

[Yo pappy]

Maybe they were all banging each other. Ever thought of that?

 

[markdabomb22]

What if you dont need senju dna to use these techs....

 

[lol99]

you kidnap a senju and then you will have a lot of dna for everyone

 

[gordo1]

TOBI said that u need senju cells. and we all know that he is a liar

Yeah, I don't really value Tobi's word too highly.

 

[abhiraj]

What if you dont need senju dna to use these techs....

Exactly.
Itachi used izanami, and i don't think he would ever try and get Senju DNA

 

[SilverSlick]

Tobi is a descendant of both. Tobi had a Uchiha father and a Senju mother. Simple as that. Don't make me tell you how babies are born. Just a theory though.