Heart disease is not a one- or two-gene problem," says Steven Ellis, a Cleveland Clinic cardiologist. Ellis oversees a genetic study that collects DNA samples from patients who enter hospitals with atherosclerosis. Ellis, like most cardiac researchers, suspects that dozens of genes contribute to a predisposition to heart disease. Of the several dozen genes, each may contribute just one percent to a person's total risk-an an amount that may be compounded or offset by outside factors like diet. As one doctor commented, any person's heart attack risk is "50 percent genetic and 50 percent cheeseburger.