Tuesday, August 11, 2009

Single Molecule Sequencer Reads Human DNA in Four Weeks

Filed under: Genetics

As we've reported in the last few years, Helicos BioSciences out of Cambridge, MA has been working on a revolutionary new method of sequencing DNA molecules. The technique does not require any cloning, amplification or ligation to be performed, but uses a novel combination of physics, chemistry, and computer vision to identify base pairs at an unprecedented speed. This week researchers from Stanford University and Howard Hughes Medical Institute are reporting the sequencing of an entire human genome using a Helicos machine within four weeks at a cheap cost of only $50,000.

The basics of the technology from Helicos BioSciences:

Within two flow cells, billions of single molecules of sample DNA are captured on an application-specific proprietary surface. These captured strands serve as templates for the sequencing-by-synthesis process:

Polymerase and one fluorescently labeled nucleotide (C, G, A or T) are added.

* The polymerase catalyzes the sequence-specific incorporation of fluorescent nucleotides into nascent complementary strands on all the templates.
* After a wash step, which removes all free nucleotides, the incorporated nucleotides are imaged and their positions recorded.
* The fluorescent group is removed in a highly efficient cleavage process, leaving behind the incorporated nucleotide.
* The process continues through each of the other three bases.
* Multiple four-base cycles result in complementary strands greater than 25 bases in length synthesized on billions of templates—providing a greater than 25-base read from each of those individual templates.

More about the announcement from Ars Technica...

Stanford press release: Professor sequences his entire genome at low cost, with small team...

Article in Nature Biotechnology: Single-molecule sequencing of an individual human genome

Product page: HeliScope™ Single Molecule Sequencer

Flashbacks: Helicos BioSciences Sequences Entire Genome from a Single Molecule of DNA; High Speed Sequencing of Single DNA

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