DNA actually proofreads itself in some cases. So this would prevent change.
"DNA actually proofreads itself in some cases. So this would prevent change."
Oh, my. Yes, DNA most often replicates accurately, but not always. That's why you don't look exactly like either of your parents, you see. That's variation. It's one of the amazing things about sexual reproduction. There is an almost endless variety available, even from just two parents.
Now, just suppose both of your parents had rather short fingers, but you expressed a genetic trait that meant you ended up with long, slender fingers, something that happens all the time. This is really simple, so I know you'll be able to follow along.
Your parents, with their short fingers, would have been very poor at becoming concert pianists, while you might well excel at that, having the long, slender fingers required. Or, perhaps a concert violinist.
Now, imagine a world where concert pianists and violinists made a great deal of money, thereby attracting mates who liked success. Your offspring would be more likely to have those long fingers, and be more likely to be concert pianists or violinists, thereby becoming successful and mating successfully. More long fingers. More success. This is variation.
You are not a clone. You are a wierd blend of genetic characteristics that melds the genetic material of countless generations in your line of descent. When something pops out that helps you succeed, you attract better mates. Eventually, everyone in your line may have longer and longer fingers, and become a species of pianists or violinists that cannot breed with short-fingered plebes.
Can you tell me why the banana industry is currently in a panic? (Hint: it has to do with imperfect genetic replication, or the lack thereof.)