Board Thread:Theories and Speculation/@comment-5012682-20150620162706/@comment-2140588-20150620171538

Kekkei Genkai are genetic, not the natures. I would safely assume that to use the kekkei genkai you would need to go through some Nature training first.

Also, if genetics were the case, Tsunade would have all the natures, giving her grandfather is Hashirama.