I don't know anything about DNA, but I don't think God anoints one child over another and says, this one is going to be talented and this one isn't. Proust is all desire. How many people could totally isolate themselves for half their lives, and be that focused. I think it's too easy to say some people are born with talent. If you have a burning desire to communicate and to be well known, and you're intelligent enough to find your style, and able enough to arrange your life so as to do so much work, and selfish enough to put it first, then the talent is there.
Talent is created.
So if students continue to work seriously, no matter how long it takes, I won't give up on them. I have so many cases of people who apparently didn't have any talent at all, were told that, and five years later they are totally different writers. People are conflicted. The most successful writers are conflicted. They make a pact with the Devil.