Oh dear, the CND does sound quite evil!
I'm doing a PhD in DNA reapir. But I would also swap with a friend of mine who is looking at the behaviour of bats (plus, they hibernate- time off for her!). My brother is studying ship construction and is trying to work out how to kill off marine life in large volumes of ballast water to avoid contaminations. There are many interesting topics out there, I wasn't hellbent on doing DNA repair, developmental biology would have been just as fine for me. My maths isn't that great, so I probably wouldn't want to do a topic that involves too much of it (but I'd lear it if I had to for my project).