Grades and Predoctoral NIH Grants
Each NIH grant comes with extensive guidance. For the Ruth L. Kirschstein National Research Service Award Individual Predoctoral Fellowship to Promote Diversity in Health-Related Research the guidance says


  Note that scores for standardized exams (e.g., MCAT, GRE) as well as a listing of the applicant’s courses and grades must be included in the Fellowship Applicant Biographical Sketch, and NOT in this attachment.


The guidance also says


  Follow the instructions in the SF424 (R&amp;R) Individual Fellowship Application Guide to ensure you complete all appropriate “optional” forms.


SF424 (R&amp;R) refers you back to PA-14-148.

In general, it is advisable to talk to the Program Officer at the NIH whenever you are considering applying for a grant/fellowship. They are more than happy to help navigate you through the submission process and generally can provide you with invaluable insight about how to improve your application. Each institute at the NIH and each funding mechanism has a different Program Officer, but they are generally pretty easy to find online.