Smokers are twice as likely as non-smokers to have damage to a critical gene that helps protect the body from cancer, according to a study in today's New England Journal of Medicine. Researchers at Johns Hopkins University are speculating that the carcinogens in tobacco smoke attach themselves to the p53 gene's genetic material and disable the cell, causing mutations. TIME medicine writer Christine Gorman said, "This is the smoking gun. All of the evidence is overwhelming. . . Unless you are a tobacco executive there is no doubt that smoking causes cancer."