Gene-poor chromosome 13 sequence completed 1/4/04. By the Wellcome Trust Sanger Institute Researchers from the Wellcome Trust Sanger Institute have completed the sequence of human chromsome 13.

Among the genes identified using the sequence of chromosome 13 are those that can dispose to breast cancer (BRCA2) as well as regions associated with schizophrenia and one containing a gene implicated in asthma.

One of the most remarkable results is just how few genes there are on chromosome 13 - although for the first time, researchers have used methods to predict the locations of a class of genes - so-called microRNA genes - which are important in controlling the activity of other genes.

The high-quality sequence consists of more than 95.5 million letters of DNA code. Painstaking study shows that, within that sequence, lie only 633 genes - fewer than on chromosome 22, which is less than half the size of 13. The findings are published in the 1 April 2004 issue of Nature.

Andy Dunham, leader of the team at the Wellcome Trust 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."

So the wilderness of chromosome 13 has revealed a bounty of new and exciting detail. Recently developed tools and databases allowed the team to look deeper into regions that might previously have been thought to be barren - junk DNA.

MicroRNAs do not specify proteins, but bind to other RNAs and diminish their activity or even lead to their destruction. This is a level of control of genetic activity that was not widely recognised only two years ago. Today, several hundred genes for these RNAs are thought to be present in the human genome.

Image credit: Wessex Regional Genetics Centre

Further reading

Dunham A et al. (2004) 'The DNA sequence and analysis of human chromosome 13.' Nature. 428: 522-528. Abstract