Editing DNA sequencer (section)

==History==

The first [[DNA sequencing]] methods were developed by Gilbert (1973)<ref name="Gilbert 1973">{{cite journal |vauthors=Gilbert W, Maxam A |title=The Nucleotide Sequence of the lac Operator |journal=Proc Natl Acad Sci U S A |volume=70 |issue=12 |pages=13581–3584 |year=1973 |pmc=427284 |pmid=4587255 |doi=10.1073/pnas.70.12.3581|bibcode=1973PNAS...70.3581G |doi-access=free }}</ref> and Sanger (1975).<ref name=Sanger75>{{cite journal |vauthors=Sanger F, Coulson AR |title=A rapid method for determining sequences in DNA by primed synthesis with DNA polymerase |journal=J. Mol. Biol. |volume=94 |issue=3 |pages=441–8 |date=May 1975 |pmid=1100841 |doi=10.1016/0022-2836(75)90213-2 }}</ref> Gilbert introduced a sequencing method based on chemical modification of DNA followed by cleavage at specific bases whereas Sanger's technique is based on [[dideoxynucleotide]] chain termination. The Sanger method became popular due to its increased efficiency and low radioactivity. The first automated DNA sequencer was the AB370A, introduced in 1986 by [[Applied Biosystems]]. The AB370A was able to sequence 96 samples simultaneously, 500 kilobases per day, and reaching read lengths up to 600 bases. This was the beginning of the "first generation" of DNA sequencers,<ref name="Metzker"/><ref name="Hutchison, C. A. III. 2007 6227–6237"/> which implemented Sanger sequencing, fluorescent dideoxy nucleotides and polyacrylamide gel sandwiched between glass plates - slab gels. The next major advance was the release in 1995 of the AB310 which utilized a linear polymer in a capillary in place of the slab gel for DNA strand separation by electrophoresis. These techniques formed the base for the completion of the human genome project in 2001.<ref name="F. S. Collins, M. Morgan, and A. Patrinos 2003 286–290"/> The human genome project spurred the development of cheaper, high throughput and more accurate platforms known as Next Generation Sequencers (NGS). In 2005, [[454 Life Sciences]] released the 454 sequencer, followed by Solexa Genome Analyzer and SOLiD (Supported Oligo Ligation Detection) by Agencourt in 2006. Applied Biosystems acquired Agencourt in 2006, and in 2007, [[Hoffmann-La Roche|Roche]] bought 454 Life Sciences, while Illumina purchased Solexa. Ion Torrent entered the market in 2010 and was acquired by Life Technologies (now [[Thermo Fisher Scientific]]). And [[BGI Group|BGI]] started manufacturing sequencers in China after acquiring [[Complete Genomics]] under their [[BGI Group|MGI]] arm. These are still the most common NGS systems due to their competitive cost, accuracy, and performance.

More recently, a third generation of DNA sequencers was introduced. The sequencing methods applied by these sequencers do not require DNA amplification (polymerase chain reaction – PCR), which speeds up the sample preparation before sequencing and reduces errors. In addition, sequencing data is collected from the reactions caused by the addition of nucleotides in the complementary strand in real time. Two companies introduced different approaches in their third-generation sequencers. [[Pacific Biosciences]] sequencers utilize a method called Single-molecule real-time (SMRT), where sequencing data is produced by light (captured by a camera) emitted when a nucleotide is added to the complementary strand by enzymes containing fluorescent dyes. [[Oxford Nanopore Technologies]] is another company developing third-generation sequencers using electronic systems based on nanopore sensing technologies.