Know your audience. With a smart phone you should be able to figure out who your interviewer is, where and when they went to school and in what subject area (not all interviewers are physicians and some will be very old). From there you should be able to tailor your presentation. If you are being interviewed by a PhD histologist you can go into different detail than if you are being interviewed by a bioethicist or an 80 year old psychiatrist. Some interviewers will want to see how well you can speak to patients and so will ask you to describe your research in terms that a child or a lay person can understand. Again, take your cue from the interviewer.
Better to say too little and be asked a follow-up question than to go on too long and bore your audience. I'd say that 30 seconds (the length of a TV commercial) should be the right length to start. I'd go with "We are interested in knowing more about ___. We use _[technique]__ to [verb] [object]. We hope that this may advance the field of ___. I've learned how to___. I found _[describe failure]__ to be very frustrating but when _[describe success]__ I felt the thrill that goes with discovery." Don't memorize this speech but some of these sentences should cover what you want to convey.