Among genome watchers, most remember the end of the Human Genome Project as a summer day in 2000. U.S. President Clinton and British Prime Minister Tony Blair appeared on TV screens around the world, lauding the completion of the first high-quality draft of the human genome. This was actually the 97 percent version of finished, the best that sequencing machines full of capillary tubing could do.

A much smaller fanfare greeted the actual completion of the project. The last chapter of the 100 percent-finished version was published in a recent issue of the journal Nature. It consisted of chromosome 1, the largest human chromosome of all. And as the one implicated in the most genetic diseases, chromosome 1 should prove the richest mining ground for biotech companies.

Since the summer of 2000, geneticists have polished the rough draft with a human touch: playing with their full gambit of laboratory techniques to tease out where sections of Gs, Cs, Ts, and As are missing and how they can be filled in. They have annotated and described the known genes along the chromosome’s length. “When [the scientists] have tried everything they know how to do, then they say they’re done. And we’re done now,” says Kris Wetterstrand, a senior program analyst at the U.S. National Human Genome Research Institute (NHGRI).

“[The final sequence is] a catalyst for our gene discoveries,” says Brian Schutte, associate professor at the University of Iowa. He and his team localized the gene for a rare type of clefting disease to a region of the chromosome, but previously had no idea which genes lay in this region. He says the Human Genome Project’s sequencing efforts greatly facilitated this achievement.

As the Human Genome Project wrapped up, NHGRI funded another project called the HapMap, and is now involved with a third major undertaking called ENCODE (the Encyclopedia Of DNA Elements). The idea behind ENCODE is to identify functional parts of 1 percent of the genome, and try to scale up once the best techniques for doing this are unearthed.

“The sequence gave us the order of the bases, then the HapMap gave us a map of common variations among different humans and different populations, which is very helpful toward identifying disease-related genes,” explains Ms. Wetterstrand. “And the HapMap is one step more basic than ENCODE.”

Understanding the genome, all researchers agree, is far from over.