Some DNA sequencers can be also considered optical instruments as they analyze light signals originating from fluorochromes attached to nucleotides.

Therefore, these sequencers can also be used in the genotyping of genetic markers where only the length of a DNA fragment(s) needs to be determined (e.g. microsatellites, AFLPs).

DNA samples can be prepared automatically in as little as 90 mins,[5] while a human genome can be sequenced at 15 times coverage in a matter of days.

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.

[4] 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, 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 started manufacturing sequencers in China after acquiring Complete Genomics under their MGI arm.

454 utilizes the detection of pyrophosphate released by the DNA polymerase reaction when adding a nucleotide to the template strain.

In 2009, Roche launched the GS Junior, a bench top version of the 454 sequencer with read length up to 400bp, and simplified library preparation and data processing.

A disadvantage of the 454 system is that it is prone to errors when estimating the number of bases in a long string of identical nucleotides.

[17] Such as, Illumina produces a number of next-generation sequencing machines using technology acquired from Manteia Predictive Medicine and developed by Solexa.

[19] Illumina makes a number of next generation sequencing machines using this technology including the HiSeq, Genome Analyzer IIx, MiSeq and the HiScanSQ, which can also process microarrays.

At its release the HiSeq 2000 provided one of the cheapest sequencing platforms at $0.02 per million bases as costed by the Beijing Genomics Institute.

[10] Life Technologies (now Thermo Fisher Scientific) produces DNA sequencers under the Applied Biosystems and Ion Torrent brands.

After five upgrades, the 5500xl sequencing system was released in 2010, considerably increasing read length to 85bp, improving accuracy up to 99.99% and producing 30G per 7-day run.

[42] MGI produces high-throughput sequencers for scientific research and clinical applications such as DNBSEQ-G50, DNBSEQ-G400, and DNBSEQ-T7, under a proprietary DNBSEQ technology.

[43] It is based upon DNA nanoball sequencing and combinatorial probe anchor synthesis technologies, in which DNA nanoballs (DNBs) are loaded onto a patterned array chip via the fluidic system, and later a sequencing primer is added to the adaptor region of DNBs for hybridization.

[46] MGISEQ-2000 was used in single-cell RNA sequencing to study the underlying pathogenesis and recovery in COVID-19 patients, as published in Nature Medicine.

[47] Current offerings in DNA sequencing technology show a dominant player: Illumina (December 2019), followed by PacBio, MGI and Oxford Nanopore.