Abstract

Researchers summoned a Baltimore County woman to an office at the Johns Hopkins School of Public Health last spring to tell her the bad news. They had found a genetic threat lurking in her 7-year-old son's DNA—a mutant gene that almost always triggers a rare form of colon cancer. It was the same illness that led surgeons to remove her colon in 1979. While the boy, Michael, now 8, is still perfectly healthy, without surgery he is almost certain to develop cancer by age 40.This genetic fortune-telling was no parlor trick. It was the product of astonishing advances in recent decades in understanding how genes build and regulate our bodies. And as scientists pinpoint new genes and learn to forecast the onset of more inherited disorders, millions of people are likely to demand their medical prognosis.