Ion Torrent Sequencing

Ion torrent semiconductor sequencing is a method of DNA sequencing that is based on the detection of hydrogen ions, which are released during the polymerization of DNA. This is a method of sequencing by synthesis, during which a complementary strand is built based on the sequence of a template strand. A microwell containing a template DNA strand to be sequenced is flooded with a single species of deoxyribonucleotide triphosphate (dNTP). If the introduced dNTP is complementary to the leading template nucleotide, it is incorporated into the growing complementary strand. This causes the release of a hydrogen ion that triggers an ISFET ion sensor, which indicates that a reaction has occurred. If homopolymer repeats are present in the template sequence, multiple dNTP molecules will be incorporated in a single cycle, which leads to a corresponding number of released hydrogens and a proportionally higher electronic signal.

This technology differs from other sequencing technologies in that no modified nucleotides or optics are used. Ion semiconductor sequencing may also be referred to as:
  • Ion torrent sequencing;
  • pH-mediated sequencing;
  • Silicon sequencing; or
  • Semiconductor sequencing.