dude do a search, and you can read about this for hours on sdn.
Most q's are straightforward, but some have difficult wording, are lengthy, and will test your knowledge of conceptual or sometimes specific points. The wording won't trick you, but may present you with a scenario, and you will have to use your previous knowledge to asses the situation and respond with the best possible answer.
I've never seen this question, but I seen plenty of people talking about a question on FRAP on sdn, which is supposed to be extremely random and difficult to answer (even if you have studied the method).
These random q's will be only like 5 q's, so I wouldn't stress it, just know your stuff in and out!
I'd study princeton reviews hyperlearning for bio , and barron's ap bio. Princeton book is verryyyyy conceptual, and you will UNDERSTAND the material afterwards. Those "harder qs" are ones which will test your understanding, rather than recall of the material.
Now I should be writing a lab report, and you should be studying lol
Good Luck studying