Entire Genome Sequencing from Single Molecule DNA

Cambridge based Helicos Bioscience announced the publication of a report in Science Magazine demonstrating the first single molecule sequencing of an organism (M13 virus genome) examining more than 280,000 strands of captured DNA.

Helicos’ uses a proprietary form of sequencing-by-synthesis called True Single Molecule Sequencing(tSMS)™. Unlike other methods, the technique builds up the sequence of each strand of DNA one base at a time.

New Microarray technology replacing PCR and speed up HTS

Dr. Richard Gibbs, director of the Baylor College of Medicine Human Genome Sequencing Centre and his researchers along with the help of  NimbleGen Systems the  company recently acquired by Roche Applied Science has developed a new technique that combines gene chip technology with the latest generation of gene sequencing machines to allow fast and accurate sequencing of selected parts of the genome

 The technology, called “sequence capture,” enables fast and accurate enrichment of thousands of selected genomic regions, either contiguous or dispersed, such as segments of chromosomes or all genes or exons uses , The study had uses NimbleChip™ microarrays in preparation for a high-throughput 454 Sequencing™.

The study Direct Selection of Human Genomic Loci by Microarray Hybridization presented on October 10, 2007, at the J. Craig Venter Institute’s Genomes, Medicine, and the Environment (GME) conference, Roche NimbleGen and 454 Life Sciences, working with Dr. Richard , will create a whole-genome human exome (all exons) microarray, with the goal of resequencing the entire human exome faster and cheaper.

Till now researchers relied upon PCR for selection of specific genomic regions for resequencing

Limitations of PCR  meant the length of sequence it can amplify was small, is difficult to scale or multiplex for the enrichment of thousands of fragments, and has limited performance in the repetitive regions typical of complex genomes, such as human.

The sequence capture microarray technology bridges the gap between next-generation DNA sequencing technology and current sample preparation methods by providing an adaptable, massively parallel method for selective enrichment of genomic regions of interest.

The new process is simpler, more accurate and efficient than the multiplex PCR . In one experiment, more than 6,400 exons (the part of the genetic code that carries the instructions for making proteins), were analyzed. Using the old technology this would have taken at least six months.

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