Electrical DNA Sequencing unveiled

A light-free DNA sequencing method harnesses the same semiconductor manufacturing technology used to make computer chips and could lead to low-cost, fast, and portable genome sequencing, according to Jonathan M. Rothberg and coworkers at Ion Torrent, part of Life Technologies. The team reports a variation of sequencing by synthesis that uses semiconductor devices to electrically detect hydrogen ions released by DNA polymerase during DNA synthesis (Nature,DOI: 10.1038/nature10242). Each chip in the Ion Torrent system contains 1.2 million wells aligned with its own ion-sensitive field-effect transistor. A typical run takes two hours and generates 25 million bases. Rothberg and coworkers used the method to generate sequences of three bacterial genomes, using one chip per genome. They collected enough data so that each base was sampled five to 10 times (five- to 10-fold coverage), enough to make the results statistically valid, with accuracy as high as 99.99%. To show that they could also sequence human genomes, the Ion Torrent scientists sequenced the genome of Gordon E. Moore, of Intel and Moore’s law fame. For 10-fold coverage of Moore’s genome, the researchers used approximately 1,000 chips totaling about 1 billion sensors.