Applying while doing pre-reqs

Is it possible to apply to various schools while you are still doing pre-reqs? For instance, MSU requires physiology. I’ve already finished biology, chem, ochem, and physics. I’ve already taken the MCAT. Do I have to wait until the following year to apply because I’m taking physiology now AFTER the MCAT?

Yes, you can apply while you are still taking pre-reqs. When you fill out your AMCAS, you can list the classes you will be taking the next academic year and mark them as “current/future coursework”. I had to do that with a couple of classes.
Typically, what will happen, is that as long as you are only short a couple of classes and indicate that you are taking them, they will not even be mentioned during the interview process. If you are accepted, you will usually receive a letter stating that you have been accepted on the condition of having completed all requisite coursework successfully. You will also have to submit copies of transcripts prior to matriculation.

Geoff, you definitely don’t need to wait to complete all the prereqs before applying. I do think it’s advisable for folks to have completed MOST of the prereqs, or the commonly-required courses (the bio, physics, chem and o-chem that you’ve done). Every once in awhile someone asks if they can apply before they’ve taken o-chem, for example. Well, yeah, you CAN but your application probably isn’t going to get the careful consideration it deserves. But in your case, you’re talking about additional required coursework above and beyond the “basic package,” and I think your plan is fine. The school certainly understands that people don’t want to wait an entire additional year.

Indeed you can, and in fact, I did not even complete all the required basic courses before I took the MCAT. I got interviews and acceptances, but those acceptances were contingent on me finishing the course with a minimum grade.
Go for it!