The human genetic code is now exposed for all biologists to see. Excluding hard-to-penetrate regions, 99% of the human genome has been sequenced. The order of its bases has been decoded as much as possible given current technologies. As such, this new sequence will be of much greater value than a draft sequence produced 2 years ago and makes it easier for researchers to find not only genes but also bits of DNA that help regulate gene activity.
The International Human Genome Sequencing Consortium got started a decade ago, when sequencing was in its infancy. In 1998, a mad scramble began after Celera Genomics in Rockville, Maryland, boasted that it would be the first to sequence the human genome. Celera and the consortium published their drafts of the sequence simultaneously in 2001 with much fanfare (ScienceNOW, 12 February). Although 90% of the bases were then known, the order of quite a few was not yet confirmed, and many gaps existed. Only the consortium took on the harder task of filling the gaps and making sure all the identified bases were in order.
Sequencers in the United Kingdom, United States, Japan, and other countries announced today that the human genome was sequenced and 10 times more accurate than they had initially hoped. In the United States, the announcement was part of a U.S.-sponsored symposium organized in Bethesda, Maryland, to recognize the 50th anniversary of the discovery of the double helix (Science, 11 April, p. 277). The sequencing of the human genome involved hundreds of researchers around the world, with five centers taking on the lion's share of the work (see chart). But now, 2 years ahead of schedule, all that's left are hard-to-assess regions such as the centromeres and long repetitive stretches of DNA. Although the consortium still doesn't have a firm grip on the number of genes in the genome, it estimates that there are about 30,000.
Genome in hand, researchers will learn many things, such as how the nature of DNA influences gene function. Moreover, as genomes of other animals are sequenced, “there will be a lot of biology that will be clarified,” says Tom Pollard, a cell biologist at Yale University in New Haven, Connecticut. For those reasons, he adds, “hats off to the consortium.”