Syd, just know your major disorders. Most of the genetics questions I got were translocations or whether something was autosomal dominant, recessive, X-linked, etc.
I had 2 pedigrees that I had to determine mode of inheritance.
Our genetics professors gave us a USMLE study packet that was very good. 30 pages long. It summarized all the major disorders. Some of the hints they gave us were useful for the exam. See if your geneticists have a similar packet.
Our geneticists told us that many of the disciplines on the USMLE are cross referenced. For instance, if you get a question asking about protein translation, then that would be counted as biochemistry, genetics, and cell biology. If you get a question relating Down syndrome with increased Alzheimer's, then that would be counted as genetics and pathology and perhaps epidemiology.
Don't freak out over genetics. The Kaplan home study program (if you're doing that) covered cell bio and genetics very well. BRS Path also had a very useful genetic disorders chapter. Don't overlook the genetic immunodeficiency disorders! Those have always been favorites on the USMLE so I've heard.
Good luck on your quiz!