What are the chances of becoming Bi Polar?

Out of curiosity, what are the chances of becoming Bi Polar if you have no immediate family (parents/siblings) suffering from it?. I am 26 and have anxiety that appears to run in my family a bit. (ocd and such issues) and I often think catastrophic thoughts like "What if I become Bi Polar?" I've never had depressive episodes. I am prone to having a nasty temper but my mother does as well and she isn't suffering from BPD. I've been around severe Bi Polars and knew one who killed himself. I'm sure that this feeds my irrational fear. And also hearing about people like Catherine Zeta Jones getting diagnosed at 40 with it rather makes me nervous.(not sure if she was genetically pre-disposed or not).