<p>There is very little causal relationship between GPA and research experience, only correlation: students with great GPAs have the work habits that enable them to also succeed in research (and vice versa). I did terrifically in courses relevant to my research, and I learned a lot of useful information. However, none of that contributed to my research success; if anything, enjoyment of performing labwork and plain, old persistence and were the major factors.</p>
<p>And no one is telling you to slack off in classes for the sake of research. Rather, if so much effort has to be put in to maintain a good (~3.5) GPA and to obtain good research experience, then any EXTRA time you have is better spent on turning good research into great research, NOT on turning a good GPA into a great GPA.</p>