I want to research genes in relation to IQ/personality. Am I even on the right U/G course? Should I be doing Molecular Cell Biology, for example? I am not sure. Should I do a PhD in Pop. Genetics? I have just been looking at a jobs site, and it looks like I could go in several directions, so which is best? If I choose a path, how adaptable will my qualifications be? I do not want to be stuck on a wrong line.

you'll probably need to do some kind of degree in biology, probably genetics/biochemistry - to be honest it probably doesn't matter hugely. The area of your postgrad will probably be a bit more important. remember it's not specific knowledge they're looking for, but to be able to see that you would be a diligent/interested researcher