In the 21 October 2004 issue of Nature (Vol. 431, No. 7011, see pp. 931-945, 927-930, and News & Views) an international consortium will publish its analysis of the completed sequence of the gene-containing portion of the human genome. Another, related study cautions that a commonly used genome-sequencing technique may not be as accurate as was thought.
In February 2001, the International Human Genome Sequencing Consortium (IHGSC) and private company Celera both announced that they had completed drafts of the human genetic sequence. But at that time, both were missing big chunks of sequence and some parts were misassembled.
The updated IHGSC sequence contains only 341 gaps, covers 99% of the gene-containing portion of the genome and contains an error rate of one per 100,000 bases. Analyses of these data reveal new features of the genome. For example, they refine the estimate of the total gene number to between 20,000-25,000 genes, and find that 1,183 of these have been very recently acquired by duplication of an existing gene .
In a second paper, Evan Eichler and his colleagues compare the most recent sequence with an earlier draft of the genome produced by Celera. They find that the 'whole-genome shotgun' sequencing technique, which was used by Celera and is now used by many research groups, fails to pick up many duplicated regions, and so may not provide a true picture of an organism's genome.
The shotgun technique involves blasting apart the genome, sequencing random fragments and then piecing them together by computer. The authors suggest that it would be better to combine this method with a more traditional technique, in which sections are sequenced in order.
Geneticists will next have to start deciphering the remaining portion of the genome that does not contain genes, says Lincoln Stein in a related News and Views article.
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Adam Felsenfeld (US National Institutes of Health, National Human Genome Research Institute, Bethesda, MD, USA)
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Francis S Collins (NIH, National Human Genome Rsh Inst, Bethesda, MD, USA)
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Evan Eichler (University of Washington, Seattle, WA, USA)
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Lincoln Stein (Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA)
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Message posted by: Trevor M. D'Souza