(FORTUNE Magazine) – You can't blame John Todd for seeming a little cranky these days. The University of Cambridge geneticist has spent years searching for the 20 or so genes thought to play a role in type 1 diabetes. If he had a decent map of the human genome, he could find those faulty bits of DNA more quickly and figure out how they work. But when Celera Genomics and the publicly funded Human Genome Project each unfurled a version of the genome last winter, the maps did not include a region that Todd believes contains a diabetes gene. He'd been handed a treasure map without the X. "This 'draft' is still a long way from being finished," he groused at a genomics trade show in San Francisco last February.

Geneticists across the country are echoing Todd's frustration; current versions of the genome map--despite all the hoopla and grand talk--aren't yet thorough enough, they say. Only about a third of the publicly funded draft is completely finished. Whole patches are still out of order, backward, or even contaminated with genes from other organisms that were used in the sequencing process. Celera's version may be in somewhat better shape, but both drafts contain missing pieces whose size can only be estimated. There's no question, says Graeme Bell, a molecular biologist at the University of Chicago's Howard Hughes Medical Institute, that some of the breaches are plenty large enough to hide a number of valuable genes.

Faced with an incomplete map, some researchers--particularly those backed by big pharmaceuticals companies--are spending their own money to fill in the blanks and resequence garbled gene data. Smaller biotech firms, entrepreneurs, and many medical school researchers don't have that luxury; they can only wait for the completed version. "I can't stress enough how crucial it is that they finish," says geneticist Colin Collins of the Cancer Research Center at the University of California at San Francisco. Not doing so, he says, would be like going to the moon and deciding not to land.

Unfortunately, mapping efforts are likely to stay in orbit for a while. The work that remains to be done is even tougher, more detailed and tedious than what has been accomplished so far. Some scientists in the trenches worry that sequencers might be sidetracked by other projects. "I get a little frightened," says Bell, "when I hear that they've already started sequencing the rat genome, the mouse, and the fish when there's still so much left to do on the human."

Not to worry, insists Francis Collins, director of the National Human Genome Research Institute and leader of the consortium that put together the public sequence. He swears that his team will complete a final map of the human genome within two years. "It's our top priority," he says. "We haven't seen signs that anyone's backing away from that end, but if we did we could take their funding away. We would do that if we had to."