I recommend taking genetics in second term. I didn't, but I wish I had. Lots of people took it, since it's a light workload and opens up an elective spot in 3rd year.
Some people also took linear algebra, and people who hadn't taken phys 1B03 had to take that.
If you don't want to take genetics, I'd recommend another course with a very light workload! Socsci 2P03/2O03 (whichever is second term) and Health St 2D03 (or whatever the new course code is), are good elective courses that people took. Second semester has a much lighter workload than first, so you don't NEED a light elective, but why not?