Medical scientists usually need a doctorate degree in biological science. Some medical scientists have medical degrees. Medical scientists typically complete courses in biology, chemistry, physics, engineering, mathematics, and computer science.
Status: Medical Student (Accepted) AMCAS states that it usually takes ~4-6 weeks for verification to go through, but looking at the verification trend right now here: http://forums.studentdoctor.net/threads/2014-2015-verification-thread.1076112/ I would say you're looking at 3-4 weeks from the time of submission.
Letters sent through the mail can take up to 15 business days from the date of receipt to be matched to the appropriate application. You must include both the AAMC ID and the AMCAS Letter ID found on the Letter Request Form when sending letters, regardless of how the letter will be submitted.