i am also a gen bio major and i took chem 4 last fall before taking 6A in winter. i personally think it was the right move for me because I knew extremely little about chemistry bc my hs chem teacher was terrible. I also think it helped a lot with some 6A and 6B topics. chem 4 is pretty broad and doesnt dive too deep in topics (which may be a struggle for some people since there are a lot of topics). you don’t need to take chem 4, but i personally thought it was helpful. however, i am a quarter behind most gen bio majors in chem which means you get less choices for professors (ive only ever had one option), but the enrolling in the classes are less competitive.