We all know the song and dance of “bad genes.” Most of us can sing a few bars—I know I can. Bad genes gave me bone spurs on my shoulders. Bad genes gave me bad teeth. Bad genes gave me a left dominant artery system around my heart. Bad genes are why I am the way I am, and bad genes are why I don’t even try. Here’s where I get in trouble. To me, “bad genes” sounds like the old idea of being “big...