I feel the defensive, adult behaviors of bpd personalities can be unlearned and healthy behaviors learned and applied through therapy and self understanding on one's underlying anxieties to people and situations; objectively looking at them. It's worked for me.
There ain't nothing DNA has to do with personality. I keep a journal at times and write out my subjective and objective observations. In DBT, although it was short lived therapy, we covered the emotional, rational, and wise mindedness theories. I'm learning to react NOT out of my emotional mind with responses like anger and acting out in other ways, but to step back and be rational. Recently I was able to let go of a long, online relationship which I had mistrusted. I think sometimes the borderline personality finds it hard to adjust or adapt to being independent in judgment due to his/her long patterns of co-dependency or transferring needs to others. Check out Dr. J. Young's, "Reinventing Your Life".