You wouldn't know it from the press conferences, but scientists are still far from deciphering the human genome. About 20 to 30 percent of our genetic code— containing enigmatic chunks of repetitive DNA— is difficult to read using current sequencing methods, says genomicist David Schwartz of the University of Wisconsin-Madison. The rest has been sorted out only in bits and pieces. Schwartz likens the situation to reconstructing a book whose pages have been torn, ripped, and scattered. "You're missing some pages, and some are out of order, but you tape it together and say 'Aha! It's finished! I've got the book!' No, you don't. It's far from complete."
And it may take a long time before anyone benefits from the information in those tattered pages. In theory, understanding how genes cause disease could lead to new targeted drugs or therapies. But epidemiologist Neil Holtzman of Johns Hopkins points out that many disorders— such as asthma, hypertension, and heart disease— result from some complex interactions between numerous genes and environmental factors. Even diseases caused by a single mutant gene cannot necessarily be cured, he says. For instance, researchers discovered the genetic basis for sickle-cell anemia more than 40 years ago, yet they still haven't developed a definitive treatment for it.
"I don't disagree that some of this has been overstated," says Craig Venter, whose company, Celera Genomics, developed the rapid sequencing techniques that helped nudge along the Human Genome Project. "But I think it's an important beginning. It will be viewed as a bright line in history because of what we can do now that we have this information, not just because of the information itself."