I was put on disciplinary probation on 2 separate occasions for various infractions ranging from underage drinking to disorderly conduct, and yes it does affect your application. I was accpeted on my 1st try but, I was told specifically by some institutions that I would be rejected admission solely because of these occurences. I wish i had never checked that box 🙂 But, I would recommend doing so if you had an "incident" occur. Speak with the person at your school in charge of such things and they will tell you what information they will and won't release. In my case the school told me, after I had submitted my application, that they would not include the underage drinking offenses since they were minor infractions from 4 years prior. So to answer the question, yes it affects ur app., but you can still get in, speak with a pre-med advisor, they'll tell you how to handle it.
Definately check to see if your school will release that info in any way first (Dean of Judicial Services...). Diciplinary action was taken against me because I lent my dorm key to my girlfriend so she could get me some cold medicine. I was studying in library for a micro exam. ended up i went to the ER that night for meningitis. My school decided to write me up.. bastards. Anyways, when the dean reviewed the incident, she "threw it out" and said that it would not be kept on record (my hall director had written me up originally).
i had an institutional action on my application... it came up at 4 out of 10 interviews, and only 1 didn't brush it off as unimportant. got into 6 schools. it probably depends on what exactly you did more than the fact there's something on there...