The genes have already evolved, you're just selecting for them, which doesn't take long.

The rich have access to gene editing. I seriously doubt working class Martians will. And I'm not sure that safe gene editing will get here before Mars colonies do. I could see it going either way. People will try it anyway, and some will win the lottery while others lose.

We already have gene editing. Last week's "60 Minutes" featured a young woman being cured (so far as the doctors can tell) of sickle cell anemia with gene editing.