Board Thread:Theories and Speculation/@comment-24824859-20160108012905/@comment-945885-20160108032201

There were other Ootsutsuki besides Kaguya and her children, as well, so there's no telling where some of those kekkei genkai abilities actually originated. It's also mentioned in the databook that at one point there were many different clans with the Byakugan, but that it had become nearly extinct by the time the Hyuga recognized they needed to take action to preserve it.

I'm not convinced that all kekkei genkai necessarily originated from Kaguya and her clan, but it's certainly likely that some are.

As for transplanting... the show seems to indicate a high degree of success with organ transplantation to obtain kekkei genkai, though Shin Uchiha's backstory implies that organ rejection is probably a possible problem. It's worth noting that both Kakashi and Obito share the same blood type, which might help. And, of course, Chakra has the ability to "link" individuals.

Perhaps Orochimaru's research into genetics will open up room for more of this stuff.