Pre- CRNA

The short answer is: both... BUT as I can say get high grades in your science classes. I know a lot of people (myself included) who have had to retake undergrad sciences or take grad level sciences and earn "A"s to prove they could excel in CRNA school. One program director told me science grades have been a reliable predictor of how well one will do in CRNA school. If your grades were marginal, don't worry, just save yourself some trouble and retake a class or two while the material is still fresh. Most programs want both your science and nursing GPAs to be above 3.0.

Some programs like Duke look at your overall GPA for all college courses you've ever taken. Others like WCU look at the GPA of your last 60 credits, which would be particularly beneficial if your earlier GPA wasn't so good. Some focus in on your nursing prereq/science GPA. For any of the above, a 3.5+ overall GPA is good to aim for. While most schools list 3.0 as a minimum, it seems most people that get in have above a 3.5.