Micaiah said:
Okay. Maybe I didn't make myself clear. Seebs got about the closest to what I was seeking. He showed how the bases are supposed to be replicated, and then change to make it into a function piece fo DNA. If we continue with the analogy using text, is that in principle what really happens?
It's pretty similar, at least.
How about a more precise description of how, for example, a duplication is supposed to happen. Is this a random event?
DNA is supposed to replicate. What we're seeing is errors in replication, which are indeed random. So, for instance, the way you get triploid chromosomes in humans (XXY sex chromosomes, for instance) is that one of the reproductive cells failed to split up correctly.
Mostly, that's a Bad Thing.
But... If it happens to a horse, and that horse mates with a donkey, there is a chance that you'll get a fertile mule. (In fact, this happened in the last couple of years.) If it happened a few times, mules might become a species - and a very successful one, probably!
Often, extra bits of chromosome material have no effect at all, because they aren't activated. But, they provide more space for mutations which could, eventually, by sheer chance, produce a useful effect.
But, basically, this is what's happening. It happens all the time, which is why there are now bacteria that can eat plastics that were, twenty years ago, not biodegradable. Now they are. The genetic material for the enzymes in question
did not exist a hundred years ago; it was produced by chance, but, because it was so useful, it spread and is now reasonably widespread.