What is one expected to say when asked "Tell me about yourself" in an interview?
I would stick to discussing your professional background. As Larry Ray pointed out, you are never required to discuss your partner, family, religious activities, etc. in an interview. Providing an answer like "Well, during an internship in college I decided I had a passion for BLANK and went on to pursue a career in BLANK. and started a job with BLANK company... etc." This should be perfectly acceptable to the interviewer.
First, this is not a question, but, instead, an order. Second, this is not an effective order during a job interview. This could open the door to many discriminatory areas. It is much better to ask specific questions that relate to the specific skills needed for the job. Larry Ray, Teacher and Trainer, Interviewing Skills.