Researchers from the Wellcome Trust Sanger Institute have completed a detailed study of 98.3% of the sequence of human chromosome 13. The analysis - published in Nature - shows that there are only 633 genes in this sequence - fewer than on chromosome 22, which is less than half the size of chromosome 13.
Recently developed tools and databases allowed the team to look deeper into non-coding regions to find microRNA genes, which are thought to be involved in gene regulation.
Andy Dunham, leader of the team at The Sanger Institute, said: "Chromosome 13 has a dramatic genomic landscape, in the centre of which is a huge 'desert' of only 47 genes. Normally we would expect about 180 genes in such a region of DNA."
Much remains to be uncovered: there are regions on chromosome 13 that appear to play an important role in leukaemias and lymphomas, but the genes involved have not yet been identified from the sequence - although chromosome 13 does include the well-known BRCA2 breast-cancer predisposition gene.