They aren't, if they were genetic they would be his MS abilities which is impossible because Uchiha only have 3 MS feats. They most likely belonged to Indra and were hidden somewhere. I made a thread about it.
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They are his MS Abilities. Why do you think they need to be activated by the dang MS.
Okay then answer this. What name would you give Sasukes Amaterasu orb? Or his Bow and Arrow?
Kishi was most likely going to make Sasuke an itachi clone but changed at last minute. All of Itachis moves favor his illusion abilities while Sasuke pulled the Amaterasu straw. Hence the reason Sasuke can manipulate Amaterasu while Itachi can manipulate time in Tsukoyomi.
Maybe kishi meant for the weapons to mean something else early on. But its obvious he debunked that fantasy to focus on Sasuke.
Also I'd like to add that Madara himself recieved nothing from Izuna. Obtaining EMS doesnt give you the others exact abilities. It makes your Doujutsu stronger and allows you to reach new heights without going blind. Everyone has their own type of Susano'o with diff weapons/abilities.
I dont know why people are adding more to the story that Kishi abandoned. It just doesnt exist. There is no point.