Board Thread:Theories and Speculation/@comment-945885-20200727142128/@comment-1512913-20200727201019

I agree with FF-Suzaku and I've been saying that for years. Kekkei Genkai are basically mutations of Kekkei Mora and Kekkei Mora are the original mutations caused by chakra fruits and/or from one Otsutsuki absorbing another (Momoshiki > Kinshiki)

Simply put: a chakra fruit resulted in a Kekkei Mora Rinne Sharingan, but it's not simply inheritable by means of reproduction in its pure form and it instead mutated into the Sharingan and Rinnegan respectively, while the Sharingan a Kekkei Genkai is inheritable, Rinnegan a Kekkei Mora is not. I know it was called/classified a Kekkei Genkai before, but it's most likely a simple retcon, as Kishimoto hadn't thought it through by that point. Kaguya's Ash Bones Kekkei Mora didn't get inherited by her descendants, but it instead mutated into Shikotsumyaku, which is inheritable, even though rare.