I've gotten a few requests for help on the following secondary essay prompt:
Do you have anything else to say in addition to what has already been stated in other parts of your application?
Usually the point of this type of prompt is to offer the candidate a fair opportunity to discuss any weaknesses in her application. So, if you have a genuine shortfall in your candidacy (low MCAT score or GPA, for example), this would be the place to ensure the committee sees that your deficit does not represent your true intellectual ability. Of course, avoid excuses or blaming others.
If the question is elective and you do not feel that you have anything to explain, it is okay to skip the prompt. Answering with filler will not further your candidacy.
