In a way, sequencing DNA is very simple: There's a molecule, you look at it, and you write down what you find. You'd think it would be easy—and, for any one letter in the sequence, it is. The problem ...

I was one of the first to spit into a test tube, giving up my DNA forever to learn more about my health and heredity. You know, the ones that promise to connect you with distant relatives you didn’t ...