Do a search in the forums, I think this has been talked about a few times within the past few days. But from what I can remember of what everyone was saying, the answer is no. If the grad student was actually teaching your course, and they know you well, then I believe you will be ok. However, if the course was taught by a professor and there were dicussion groups, etc led by the grad student, you may want to have the grad student write it and then the professor co-sign it.