When I get a candidate who has no sense of the job they are applying for and is not able to ask meaningful questions, it tells me they don't care or don't understand.
If you are completely unqualified for the job, you will be found out, but if the difference in skill/experience is small enough, it's probably best to be honest about the gap. In that case, "studying up" may be a risky investment of your time, but at best it may show your commitment and at worst you will have picked up some new skills :)