Yes. Generally on your applications to MD-PhD programs you talk about the research you’ve done and your possible future research interests. When you go to interviews you should have an idea of a couple labs/researchers whose work you’re interested in. In terms of which lab you actually join, generally that decision isn’t made until well into M1-M2 (sometimes even G1, and some people end up switching if a lab isn’t a good fit and that’s ok).
Your major is much less relevant than your research experience. And the program doesn’t need to know which lab you’re joining at the time of acceptance. They just need to believe in your potential.