happy to help. The question you're asking here concerns a massive chunk of biology so theres a tremendous amount to learn. If you want to learn more, the key is to take it in bite sized chunks and go at your own pace. To start, you could look at a simple case and search "explanation of the lac operon" which was one of the first systems in which gene regulation was well studied, or you could just search the term "gene regulation". Alternatively any biology textbook will have tons of information on gene regulation, even the slightly out of date ones. Finally you can check out the book "Endless Forms Most Beautiful" for a slightly lighter read, written by an expert in the field and a great science communicator. This last option might be the most enjoyable because of the digestible writing style compared to a textbook.

i'm confused, was your question about changing the dna sequence of just one protein, leaving all the rest of the dna unchanged? that's how i interpreted it. but askoemnzviwcasf seems to have interpreted the question as you changed all parts of dna that code for a protein. was their interpretation correct?