I don't think that you can update your grades to AMCAS. Once you submit your app for verification, you cannot make changes, except for address ones. If you think that your grades will help you, send the transcripts to the universities directly, or just send an update letter stating that what classes you took and your grades. I am sure that they will verify the info upon matriculation.
well, what if I send them an official transcript? they would have to change the last grades according to it. If I send it to school, that tanscript is not going to give them a science GPA. However, if time is an issue, i think it would be the best thing to do. More than that the schools would just want to see my progress and an increase in grades. If they see it, it would speak for itself. Thanks!