I thought the 5/27 test was more molecular biology than genetics. I guess if you wanted to call it all genetics, then you could derive genetics into molecular biology pertaining to gene expression and regulation versus genetics pertaining to population factors. You definitely wanted to be strong in the former for the 5/27 test.
You need to be able to read experimental protocols, interpret the abbreviations quickly, and then understand the data for molecular biology experiments. The best way to reach this goal is to involve yourself with undergraduate research. The other option is to read some Cell or Nature papers. If you can make heads and tails of that type of reading in ~30 minutes, then you probably will be ready for a test that mimics the 5/27 test.