How far would you be willing to go to satisfy your need to know? Far enough to find out your possibility of dying from a terrible disease? These days that’s more than an academic question, as Tracy Smith reports in our Cover Story. There are now more than a thousand genetic（基因的）tests, for everything from baldness to breast cancer, and the list is growing. Question is, do you really want to know what might eventually kill you? For instance, Nobel Prize-winning scientist James Watson, one of the first people to map their entire genetic makeup, is said to have asked not to be