The human genome sequence: what next?

Last week saw the publication of the entire human genetic code, around three billion base-pairs of DNA. The two draft versions, published by the  Human Genome Project public consortium and US firm Celera Genomics, are both around 90 per cent complete.

The results reveal that humans probably have around 30,000 different genes, a surprise finding given previous estimates of 50,000-100,000. One major area of post-genome research will be working out how 30,000 genes can encode the information necessary to make the estimated 250,000 different proteins found in the human body. Many scientists feel that the key to understanding human health lies in identifying all these proteins, known collectively as 'the proteome'. The Human Proteome Organisation (HUPO), an international organisation that aims to increase scientific, political and financial support for large-scale protein analysis, was launched last week.

Although the analysis of the genome shows that humans share 99.9 per cent of their genetic information, this still means that around 1 in every 1000 DNA base-pairs differs between any two people. Another article published in Nature last week reported the identification of 1.4 million human DNA variations, known as SNPs (single nucleotide polymorphisms). Working out how these differences affect human health is another major challenge facing researchers.

Genome researchers are already planning to compare the human genome to that of other species such as the mouse, to help identify crucial genes and their functions. But there have been renewed calls to sequence the chimpanzee genome in an effort to identify uniquely human genes. Chimps and humans share around 99 per cent of their DNA, and so far only one major difference has been found, reports this week's New Scientist.