Kakashi making chuunin at six always makes me wince for some reason any time I remember it. "Genius" he might be, super-intelligent kids, I can live with (child geniuses capable of achieving university level knowledge are extremely rare but thay DO happen) so him learning some jutsu and having chakra capacity to perform them at six - somewhat okay but... He was freakig SIX year old. As in small, runty, physcially EXTREMELY weak in every aspect, pure physcial strenght, power, speed, endurance - you name it.
Enchacing physical traits by chakra, okay - but you must have something TO enchance in the first place, which six year old Kakashi simply WOULDN'T have, no matter how much of a genius he might have been. And even if, and that is big if, he could overcome that with chakra, the efffect should have been similar to opening the Celestial Gates - as in ripped muscles, shattered bones, suptured tendons and all that. I'm no biology or anatomy buff, so I can't be sure, but on pure logic alone, six year old body has lots of growing to do and musculature is naturally weaker and more vulnerable. And I doubt he could have passed by ninjutsu or genjutsu alone - the way the exams are shown by Bakamoto, it is obvious that they try to test ninja in EVERY aspect.
They way Kakashi is shown, having super-acurate insight to everything, being (apparently) incredibly handsome and mysterious, being "legendary" before he hit his late teens, learning from Yondaime, creating "most powerful assasination technique aka Chidori" (which is laughable as assasination tool in my opinion simply because it makes to much fucking NOISE to be considered that), becoming chuunin at six, having a sharingan eye ,knowing fucking ONE THOUSAND jutsu (or more), knowing Yodaime's prized techniques (him knowing the Rasengan pissed me off to no end, since I saw it as Naruto's "legacy" from Yondy and his own, unique move that Sasu-gay couldn't copy - I wouldn't be surprised if Kakashi suddenly started to use Hiraishin as well) and so on... Well.. How do I put it... He seems like an SI more so that Sasuke EVER was (and THAT takes some "skill"). Poorly made, uber-god like one. As if someone tried to write an SI fic, with SI having some knowledge of Naruto and being "reborn" as Kakashi and somehow "magically" forgetting about the Kyuubi.
Hmm... Come to think of it, this almost makes me want to write a parody SI fic just like that.
And about ability being genetic, no. Just no. Why? In simplest terms, Talent might be inherited with genes you get, but talent is about ten, maybe twenty percent of the package, rest is skill, expirience and hard work. Sure, talent is CRITICAL, since without it you can't do much, but without proper conditioning and training you won't ammount to anything.