Well if you have the time take a genetics class. After my genetics class I turned a weak point into a very strong one and my bio scores reflected that. After the genetics class all the questions on the practice tests concerning genetics seemed REALLY basic.
I guess genetics is a fairly broad topic. Which topics, specifically, are most directly tested? Are we talking punnet squares or pedigrees? or are we talking more molecular bio--DNA Replication, RFLPs, etc.
As far as I remember, if you know the EK material for genetics cold, that is all you will need to know for the MCAT. I'm not sure what other source would be more detailed but I definitely would NOT suggest taking a genetics class, that is entirely overkill.
Just remember that the mcat is mainly based on lower division classes, going deep into genetics will result in a lot of useless material, I believe it might help for one or two questions it did for me but a semester/ quarter long classes for 1-2 questions seems like a waste. Work on a lot of the basics understand DNA, make sure you understand the terms there isn't much missing of EK's sections.