![]() ![]() Detection of changes in pH that provides information on the sequence of target DNA. Addition of one of four dNTPs results in the incorporation of two thymines into the elongating strand and the release of two protons. Addition of one of four dNTPs to the reaction sample results in the incorporation of one guanine into the elongating strand and the release of one proton. Lastly, the data is analyzed by a computer in order to obtain the DNA sequence of the original DNA molecule (Figure 2C). Although Ion torrent sequencing offers another rapid sequencing technology for scientists to utilize, just like with pyrosequencing, a major disadvantage is that the signal becomes less clear when repetitive homopolymer regions are being sequenced. 2,3 A greater decrease in pH indicates consecutive dNTPs being incorporated (Figure 2B). Each time a dNTP is successfully incorporated onto the elongating strand by DNAP, hydrogen ions are released resulting in a decrease in pH that is detected by the pH-sensitive chip (Figure 2A). To begin sequencing, one of the four dNTPs is added and washed away depending on if a signal is detected. emPCR to result in a magnetic bead coated with millions of copies of the same ssDNA. Binding between biotin on the ssDNA and streptavidin on the magnetic bead. Fragmentation and denaturation of the DNA and the addition of two different adapters and biotin. Afterwards, each bead is placed into a pH-sensitive chip containing thousands of wells.įigure 1: Ion torrent sequencing DNA library preparation process. 2 As a result, millions of the same ssDNA fragments are bound to a single bead (Figure 1C). 2 Next, the resulting ssDNA library is individually attached to a magnetic bead via the streptavidin and biotin interaction (Figure 1B), which is then amplified via emulsion polymerase chain reaction (emPCR). This process begins with the target DNA molecule that is being sequenced getting broken up into approximately 400 bp single-stranded DNA (ssDNA) fragments and two different adapters, alongside biotin, which are then added to the ends (Figure 1A). 1,2 Being the first to utilize this component of the naturally occurring DNA synthesis process to extract information, ion torrent sequencing ended up becoming the first sequencing technology to avoid using fluorescence or camera scanning, an entirely novel sequencing platform with numerous advantages. Under the name Ion Torrent Inc., his latest start-up at the time, Rothberg was developing another sequencing-by-synthesis technology that takes advantage of the fact that when a deoxynucleotide triphosphate (dNTP) is added to the elongating strand, pyrophosphate and a positively charged hydrogen atom is released. Jonathan Rothberg was already working on his next big invention, Ion Torrent Sequencing. After playing a pivotal role in automating pyrosequencing, the first next-generation DNA sequencing technology to successfully reach commercial markets, Dr. ![]()
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