NEXT GENERATION SEQUENCING TECHNOLOGIES
Ion Torrent Sequencing (Life Technologies Inc.)
Ion Torrent is different from other NGS sequencers, because it does not make use of optical signals. Instead, it is a very complicated pH meter: it registers the change in electrical current that comes when the addition of a dNTP to a DNA polymer releases an H+ ion .
The input DNA or RNA is fragmented to ~200bp. Adaptors are added and one molecule is placed onto a bead. The molecules are amplified on the bead by emulsion PCR. Each bead is placed into a single well on a chip.
The chip is flooded with a single species of dNTP, along with buffers and polymerase, one NTP at a time. The pH is detected is each of the wells, as each H+ ion released will decrease the pH. The changes in pH allow us to determine if that base, and how many thereof, was added to the sequence read.
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