The GPA for graduate classes is calculated separately from the GPA for undergraduate classes as is the GPA for post-bac classes. Grades from a second undergraduate degree are counted as post-bac grades (I actually argued with AMCAS about this...). Graduate classes taken at the undergraduate level are counted as undergraduate if they appear on an undergraduate transcript and graduate if they appear on a graduate transcript. The same goes for undergraduate classes taken at the graduate level (which count as graduate classes). Graduate classes taken as a post-bac are counted as undergraduate post-bac classes. (I actually have all of these situations on my transcript) All relevant classes taken at the undergraduate level, regardless of whether or not they are post-bac classes, factor into your science GPA. The science GPA classes are biology, chemistry, math and physics as defined by the title, not the subject, of the class. (AMCAS counted every class that had the words biology, chemistry, math and physics toward my science GPA, even a few that obviously didn't belong)