Finished human genome contains even fewer genes than expected 21/10/04. By the Wellcome Trust Sanger Institute The International Human Genome Sequencing Consortium has published an analysis of the 'gold standard' version of the human genome sequence, and has reduced the human gene number to 20-25 000.

The International Human Genome Sequencing Consortium has published its scientific description of the finished human genome sequence, the product of the 13-year effort to read the information encoded in the human chromosomes that reached its culmination in 2003.

The paper, which appears in the 21 October issue of the journal Nature, examines the current genome sequence, which contains 2.85 billion nucleotides, encompasses around 99 per cent of the euchromatic (or gene-containing) portion of the human genome and is 99.999 per cent accurate - 10 times more accurate than the original goal.

Notably, the predicted total number of genes has fallen to just 22 287: 19 599 known protein-coding genes and a further 2188 sections of DNA predicted to be protein-coding genes. Original estimates of gene number when the draft genome sequence was released were between 30 and 40 000, a figure that was considered surprisingly small.

"Only a decade ago, most scientists thought humans had about 100 000 genes. When we analysed the working draft of the human genome sequence three years ago, we estimated there were about 30 000 to 35 000 genes, which surprised many. This new analysis reduces that number even further and provides us with the clearest picture yet of our genome," said NHGRI Director Francis Collins. "The availability of the highly accurate human genome sequence in free public databases enables researchers around the world to conduct even more precise studies of our genetic instruction book and how it influences health and disease."

Biography: Francis Collins

'Finished' doesn't mean that the human genome sequence is perfect. There still remain 341 gaps in the finished human genome sequence, in contrast to the 150 000 gaps in the working draft announced in June 2000. The technology now available cannot readily close these recalcitrant gaps in the human genome sequence. Closing those gaps will require more research and new technologies, rather than industrial-scale efforts like those employed by the Human Genome Project.

More than 2800 researchers who took part in the International Human Genome Sequencing Consortium share authorship on the Nature paper, which expands upon the group's initial analysis published in February 2001. Even more detailed annotations and analyses have already been published for chromosomes 5, 6, 7, 9, 10, 13, 14, 19, 20, 21, 22 and Y. Publications describing the remaining 12 chromosomes are forthcoming.

Further reading

International Human Genome Sequencing Consortium (2004) Finishing the euchromatic sequence of the human genome. Nature 431: 931-45. Abstract