I am a DO student at MSU, so hopefully I can help clarify things here. 🙂
Yes, we take all our science classes in the first year with the MD students. In 2nd year we go our separate ways. The MDs have a PBL format 2nd year, whereas the DOs take lecture-based systems courses in 2nd year.
As for the passing grade: In *all* of the classes, the passing grade is *at least* 70%, regardless of whether you're DO or MD. Getting less than 70% in either school definitely means you fail.
In some classes, the passing mark was set higher than that for everyone, both DO and MD (for example, Gross Anatomy required a 75%; Pharmacology and Neuroscience required a 72%). In other classes, the passing score for DOs remained at 70%, but an MD student who received a grade between 70 and 75% received a "conditional Pass" grade that required some kind of remediation. So, basically, an MD student who receives a 70% in a class can still pass the class, but has one more hoop to jump through than a DO student who gets a 70% would and gets a "Conditional Pass" notation on their transcripts.