is this possible?

Probably it is possible but...

1.You have to take electives in bio and chem (not sure if that applies).
2.Get a high gpa this year (not sure how high).
3. I think you will be put back into first year again starting sept 2012.

Your best bet is to talk to an academic counsellor form the science department. I believe their office is in first floor BSB. Here’s their website:

http://www.science.mcmaster. ca/lifesciences/

Good luck