I know you have to be trained, but once you know how to use the chakra type, but wouldn't that include, the hand seals and how to mold the chakra? Unless you come up with the juitsu like Sauskes lighting style katana blade.
If it was a genetic trait, wouldn't the 3rds bloodline be the one Orochimaru would want. He can use all the diffrent styles in the village right?
In the link I put up, Sauskes dad says its just a basic juitsu that the Uchiha clan uses. And once you can do it your allowed to/you get to wear the clans crest, on your back. (and even thats kind of dumb fans make wind)
And sucks for Naruto, if and when he fights sauske, he'll do what he did against Danzo and use the wind element against him.
Wouldn't the sharingan be the Uchiha family/clan trait.
But if their talking metaphoricly about the Uchihas ability to manipulate the 9 tailed beast then it still makes sense. Since like fire the nine tailed beast could be helpfull or destructive depending on how its used.
And if chakra nature is determined purely by genetics how would Sauske have figured that he also was a lighting type if he was already disposed to be a fire type?
Again its weird, look at Negato during his training with Jirya he's using wind style. How would jirya teach him wind style, and Yahiko water style, and them konan is just using her regular chakra fused with paper.
Maybe the paper expresses what type comes easiest? Kakashi said a few pages later in the links Train posted that the papers expressed what nature type a given ninja is skilled with. Kakashis was lightening, but he's used water and earth, not sure about fire though