I had a nice phone coversation with adcom lady at UMDNJ about this already because I was jsut dangling on a C, C- borderline in one of my dumb upper bio elective class that I didn't care about. She asked me if the class I was struggling with was a pre-req course. I said no and she said, "if it's not a pre-req course, we don't really care. Just make sure you get your diploma by the time you enter the dental school." So I say the most important thing is that you graduate on time. C's don't bother most schools, but UOP because they strictly say that they expect B or better in all the classes you are takng.
If anyone cares, that "dumb upper bio elective" class I was taking, even though I got a C-, lol professor knew my situation and gave me a C. Wow~ what a nice guy.