The closed file may be less interested in what you have done (it is already there in black & white for the larger committee, even if the interviewer can't see it) but in what makes you tick, why you chose medicine, how you tested your interest in medicine, what other careers you considered, what you do for fun/to relax, your opinion on issues related to medicine, health and/or ethics.
"Tell me about yourself" if your opportunity to reveal the parts of yourself you want to talk about. Most people will open with their college, major, hometown, and maybe something about the experiences they'd most like to talk about (research, volunteerism, full-time job since college, summer experience). The key is to get to the point where the interviewer can say "tell me more about that". You'll want to tell a story that is interesting and engaging and tells the listener about your interests, your motivation, your ambitions. Don't fill the entire time period with a monologue but stop after a paragraph or so to give the interviewer time to ask another question.