Following the completion of the human genome sequence in April 2003 (99% of gene containing regions sequenced), researchers have released the complete sequence of the twelfth of the twenty-four different human chromosomes (twenty two autosomes or non-sex chromosomes, plus the X and Y chromosomes). The sequence of chromosome 5 has been completed to the human genome project ‘gold standard’ of 99.99% sequence accuracy by scientists from the US Department of Energy Joint Genome Institute in collaboration with colleagues at the Stanford Human Genome Center. Published in the journal Nature, chromosome 5 is the largest to be sequenced so far at 177.7 million DNA base pairs, but has one of the lowest gene densities with a total of 923 recorded genes. The researchers found non-coding sequence elements within gene-poor regions that are highly conserved between humans, chimpanzees, mice, rats and chickens, and propose that these elements regulate distant genes. Joint Genome Institute director Eddy Rubin commented: "Important genetic motifs gleaned from vast stretches of non-coding sequence have been found on chromosome five", adding: “these regions, conserved across many mammals, actually have a powerful regulatory influence" (see BBC news report). 66 of the 923 genes identified are known to be linked to human genetic diseases; a further 14 diseases are thought to involve genes on chromosome five, but as yet no specific genes have been linked with the diseases.
The sequences of remaining 12 human chromosomes are due to be completed to the same level of accuracy by the end of the year, by members of the International Human Genome Sequencing Consortium.