I know of one school that has a formula based upon your overall GPA and your MCAT score. If you don't meet their cutoff line from the formula, then they don't even look at your application or your secondary, throw all that away and cash your check.
But with my talks with most schools that I have applied to (from advisement), the most important score they evaluate is your science GPA. The idea is that your grades in those courses help to determine if you can handle the course-load in medical school. I do not know the exact details of how they correlate, but I am sure a current medical school student can go more in-depth regarding the matter.
