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Sanger and Solexa Use GAS to Sequence X Chromosome; Full Draft Genome Expected by Year End

The following update serves to correct the headline to reflect that Solexa researchers worked with Sanger staff to sequence the X chromosome. Additionally, the article incorrectly reported that the X chromosome has 15 megabases when in fact it is 155 megabases long. Finally, Solexa achieved 16-fold coverage with at least 2 fold coverage across more than 99 percent of sequenceable bases — not more than 90 percent, as the story reported.


NEW YORK (GenomeWeb News) - Solexa researchers in collaboration with the Wellcome Trust Sanger Institute have sequenced a human X chromosome using the Solexa Genome Analysis System, the company said today.

Solexa presented details of the project yesterday at the Genomes, Medicine and the Environment Conference in Hilton Head, SC. The company said it worked with Sanger researchers to sequence purified X chromosome DNA and to align 2.6 gigabases of data to the 155 megabase reference sequence.
Solexa said it plans to add more coverage to the draft sequence, but reported that so far it has achieved 16-fold average coverage with at least 2-fold coverage across more than 99 percent of "sequenceable" bases.
Solexa added that it has achieved greater than 99.99-percent coverage of sequencable exonic bases and that it was also able to confirm 96 percent of a test set of known dbSNP genotypes.
The company said it was also able to identify fragments from other chromosomes present in the sample using its flow-sorting method for purifying the X chromosome. The frequency of these fragments was around 10 percent, which is “in line with expectations for the technique,” Solexa said.
Solexa CEO John West touted the collaboration, noting that the results “validate our belief” that the Solexa platform will enable larger-scale sequencing projects in the future.
West added that the company is currently sequencing a complete human genome internally, which it expects to complete to draft level by the end of the year.

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