Experts agree on the value of genetic testing when there is a family history of disease, or if the patient has an illness frequently caused by a mutation. Knowing the disease mutation lets family members find out if they have it too and need preventive care. The book explains that doctors can order tests with genetic counseling at relatively low cost and how this will help them prescribe preventive actions, make earlier diagnoses, and get better outcomes. The book's genetic discussions also delve into the implications of broad-based genetic screening without a family history. Policymakers are considering the benefits and drawbacks of this approach and I present both sides of this debate.

While working on this book I uncovered a family secret hidden for over one hundred years. Family lore had it that a heavy dressmaker's mirror fell on and killed my uncle when he was four. But the death certificate told a different story—his true cause of death was heart failure. My grandparents fabricated the accident to protect their surviving children's marriage prospects. Long before the discovery of DNA, my grandparents intuited and feared James Watson's message, "We used to think that our fate was in our stars, but now we know that, in large measure, our fate is in our genes." The book suggests genetic testing and associated medical intervention can change our fates.