His troubles began in 2003, when he marked the fiftieth anniversary of his co-discovery of DNA’s structure by giving an interview for a documentary on PBS and the BBC. Genetic engineering should someday be used to “cure” people who have low intelligence, he said. “If you really are stupid, I would call that a disease.” It reflected his deep belief, perhaps fostered by pride in his seminal scientific discovery as well as the daily angst of living with his schizophrenic son, Rufus, in the power of DNA to explain human nature.