As others have said, it couldn't hurt. At the least, if you perform well, it'll show adcoms that you can handle "higher level" material in the biological sciences. I don't know specifics (yet) about curriculums in the first and second years of D school, but I'm sure there will be a plethora of advanced biochem.
Either way, it's a good idea to take biochem as an undergrad regardless of whether or not it comes up on the DAT.