Reading the Book of Jim

That would be especially unfortunate given that many genes linked to disease raise the risk of that disease 20 percent or 40 percent or even 200 percent—but well short of "you will definitely get it." The overall chance of getting schizophrenia, for instance, is 1 percent; a 200 percent extra risk due to a genetic variation means your risk is still just 3 percent. And the uncertainty about the consequences of having a particular gene variant is even greater for traits such as aggression, neuroticism, shyness and intelligence. Fatalism when it comes to those could be tragic, making parents give up on kids who struggle academically or resign themselves to sociopathic behavior despite reams of evidence showing that DNA is not destiny. With the spectacular advances in genetics since the discovery of the double helix, says the genome institute's Lawrence Brody, "we've convinced the public that genetics is important and deterministic. Now we have to back off a little and say it's not that deterministic."

Not even experts are immune from the sovereignty of DNA, though. Watson remains scientifically active and intellectually engaged, only occasionally forgetting a name, he says. But there is one part of his genome he has asked 454 to keep private, even from him: whether he carries gene variants associated with Alzheimer's disease. He fears that if he knew he did, he would interpret each slip of memory as impending dementia.

Coincidentally, just as the personal genome arrives, so does another novel way to detect disease early. Called biomarkers, they are proteins in the blood that reveal the presence of disease before it even causes symptoms, offering a good chance for successful treatment. The PSA test for prostate cancer is a biomarker, but others promise to be much more useful (the PSA test has not been shown to save lives). "Genetic tests just tell you you have a chance of getting this condition sometime," says Mark Chandler, chairman and CEO of Biophysical Corp., which sells a $3,500 test that screens for 250 biomarkers indicative of scores of disease. "With biomarkers, it's not just potential anymore; it's real."

Despite the concerns over its usefulness, if 454 is right about the $1,000 or even the $10,000 cost, the personal genome sequence will likely become a must-have novelty—even if for now it's just "recreational genetics," as Brody calls it, amusing but not terribly useful. As he prepared to fly to Baylor for the official unveiling of his genome, Watson expressed nary a doubt that everyone should learn the 6 billion chemical letters that spell their own genetic blueprint. "It's going to be an extraordinary period," he says. For better or worse.

© 2007