In 2007 Nobel laureate James Watson eyed his genome for the very first time. Through more than 50 years of scientific and technological advancement, Watson saw the chemical structure he once helped to unravel now pieced into a personal genetic landscape that lay before him.
There was one small stretch of DNA on chromosome 19, however, that he chose to leave under wraps. That region coded for the apolipoprotein E (APOE) gene. Since the early 1990s APOE has been a telling genetic marker of Alzheimer’s risk: certain forms of it correlate strongly with the development of the disease. Watson’s grandmother suffered from Alzheimer’s, but without any reasonable treatments or proved preventive strategies, the discoverer of the double helix decided the information was too volatile, its revelation creating more potential harm than good.