Carl Zimmer in Slate:
In June 2007, James Watson, a co-discoverer of the structure of DNA, went to Houston to pick up his genome. At a ceremonial press conference at Baylor College of Medicine, scientists handed the 79-year-old Nobel Prize-winner a DVD on which they had recorded a highly accurate reading of all the DNA nestled in the nucleus of each of his cells. There was, however, one glaring gap.
Watson spoke at the conference about the value of genomes to medical research. “I think we'll have a healthier and more compassionate world 50 years from now because of the technological advances we are celebrating today,” he declared. In addition to giving Watson his genome on a DVD, the Baylor team also put the sequence into the public database GENBANK, where scientists can download it and compare it to other publically available human genomes. But scientists will not be able to see one of Watson’s 20,000 genes. The gene encodes a protein called apolipoprotein E. A variant of the gene, called ApoE4, dramatically increases the risk of developing late-onset Alzheimer’s disease. Watson’s grandmother had died of Alzheimer’s disease, and Watson decided he would rather not know if he carried the variant.