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Scientists Analyse Key Chromosome Thu 23 October, 2003 06:25 BST By Patricia Reaney LONDON (Reuters) - Scientists in Britain have finished the final analysis of human chromosome "6" which contains genes linked to the body's immune response against bacteria and viruses. It is the largest of the 23 pairs of human chromosomes completed so far, with 2,190 genes, and forms nearly six percent of the entire human genome, or book of life. "Chromosome 6 is very rich in immune genes. These are the genes that give us protection from pathogens," said Stephan Beck, the head of human sequencing at the Wellcome Trust Sanger Centre in Cambridge, England. "They basically determine whether or not you survive if you get infected by bacteria or viruses," he told Reuters on Wednesday. The sequencing of the human genome, the complete list of coded instructions needed to make a person, was finally completed by a team of international scientists in April. Researchers are now analysing each chromosome, strands of tightly packaged DNA, to learn how to prevent, diagnose and treat diseases. "These genes on chromosome 6 are involved in breaking down small bits of the invading pathogen and presenting it on the cell surface," Beck said. The foreign bits are recognised by other cells that realise it is infected and kill it. BOOST FOR ORGAN TRANSPLANTS Beck said the immune genes are particularly important for transplant medicine because doctors will be better able to match donor organs and recipients. "These genes are absolutely critical to have good matches in transplant medicine," he said, adding that the sequence, which is reported in the science journal Nature, has also been submitted to public databases. About 1,557 genes on chromosome 6 are thought to be functional. Beck and his team have identified roughly 130 genes that somehow cause or predispose humans to certain diseases. "Most of diseases that are implicated here are complex diseases, meaning that many genes are implicated but there are single gene disorders included as well," he added. The PARK2 gene, which is involved in a form of Parkinson's disease that strikes early, and the HFE gene which is linked to hereditary haemochromatosis are also on chromosome 6. Haemochromatosis is a disorder in which people absorb excessive amounts of iron which can lead to organ damage. "It is another small mosaic stone in the run to find and analyse complex diseases. There are up to 10 and very often more genes involved in a single disease," said Beck. Chromosome 6 also has the largest cluster of transfer RNA (tRNA) which helps to translate DNA into proteins. Each chromosome is made up of a molecule of DNA in the shape of a double helix which is composed of four chemical bases represented by the letters A (adenine), T (thymine), G (guanine) and C (cytosine). The arrangement, or sequences, of the letters determines the cell's genetic code. Chromosomes 20, 21, 22, 7, 14 and Y have also been completed. SOURCE: Reuters http://tinyurl.com/s0ty * * * ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn