[Papabear47]

Question.If a particular attribute begins to develop such as feathers on early reptiles does the gene responsible for the previous skin mutate or is it replaced by the new gene.

[RadioAstronomer]

If a particular attribute begins to develop such as feathers on early reptiles does the gene responsible for the previous skin mutate or is it replaced by the new gene

I have pinged a few folk who could better answer your question. I will still do a bit of research on the answer though. :-)

[Gorjus]

does the gene responsible for the previous skin mutate or is it replaced by the new gene.

Short answer: Yes. Longer answer: It depends.

Wild Analogy: The gene sequence is like a computer code (okay, so that part is not so wild) but it's designed to run on a limited system. If you want to add a feature, you either need to modify an existing feature or delete it because there's only so much room for code. And so both of your options apply, sometimes both together. As time goes on, like computers, some better models are developed that can run larger and more complex codes. (And some creatures, like coral, don't make many modifications to their code, so they have unused bits hanging around that other creatures have had to replace or modify.)

Final observation: The way in which genes work is a lot more complex than the simple Mendeleev model. (Warning, anlogy switch coming) I think we're going to find that much of what we think of as genes are more analogous to letters than distinct blueprints for physical characteristics. As a whole, the letters form words and sentences, but the specific letters are be used in lots of places. Just because we find one word using that letter doesn't mean we understand the scope of uses for that letter.

[Junior]

Feathers (and hair) derive from the reptilian scale, not its skin.