Izanagi and Izanami do not require the Uchiha and Senju Bloodline to use. As long as the user has a Sharingan it will work, i.e. Danzo. Senju DNA included will increase the duration of Izanagi to over a minute for Danzo and five for Obito. So you see, neither Senju DNA nor Uchiha DNA is required, just the Sharingan, Senju DNA and Uchiha DNA only increase the strength of the technique. This is because Izanagi was an offshoot of the Creation of All Things technique, which was used by the Sage of the Six Paths, the progenitor of both Senju and Uchiha lineages.