Do your parents mold what kind of personality you will have?

What I mean to say is, in my case, my parents divorced when I was young, and I moved with my mom. I look a lot like my dad, but my personality (sense of humor, etc) is more like my mom. How much of our personality is hereditary and how much is "programmed" in, and is there any room for environment to affect it as much as people might think it does?