US and German scientists have published the entire genetic code of chromosome seven, the largest human chromosome to be fully sequenced so far. It is made up of 153 million letters of DNA code (base-pairs), and contains at least 1,150 genes that specify proteins. The researchers say that they include genes involved in head and face development, and white blood cell cancers, as well as previously known genes involved in deafness and cystic fibrosis. 'This work completes another volume in the genome encyclopaedia at a high standard of quality and a high degree of continuity' said team leader Richard Wilson, director of the Genome Sequencing Centre in St Louis, Missouri.
A final version of the entire human genome sequence, which consists of 22 chromosomes named 1-22, plus the two sex chromosomes-X and Y, was unveiled in April 2003. In addition to this international collaborative effort, research groups have been analysing each chromosome individually, to identify coding sequences and to study their genetic structure. The results for chromosome seven show that as well as the 1,150 genes, it contains 940 'pseudogenes': non-coding DNA sequences that look like genes, but do not specify proteins. The researchers also found that chromosome seven contains an unusual amount of duplicated material, which may play a role in the evolution of new genes. Duplicated regions were also found in a region of the chromosome that, when it is missing, causes the rare genetic condition Williams-Beuren syndrome.
Wilson said the chromosome seven analysis also revealed 'a number of genes' that are involved in human cancers such as lymphoma and leukaemia, knowledge that could help design new treatments. The researchers published their results in the journal Nature.
Sources and References
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Chromosome linked to deafness, lymphomas sequenced
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Scientists unlock secrets of largest human chromosome
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