MD schools yes, DO schools no. Texas (MD and DO, I think) counts math as science and counts computer science as math. Non-TX MD schools don't count computer science as math. (And non-TX DO schools don't count math as science.)
Varies by school, but pretty rare. UWash, for instance, used to weight (fresh + soph*2 + jr*3)/6 and ignore senior year, but apparently they don't any more.