1) It's certainly possible! All schools take into account a variety of things when considering your admission. If you do very well on the GRE, have an impressive resume, and can prove your value to the school, it doesn't matter where you went to undergrad. 2) A grad program is, for the most part, a fresh slate. You can get a PhD. in a different subject than your previous degrees with a little preparation. Your best bet is to work with professors closely and make sure you're well-prepared for your courses. Good luck!