By Sally Roberts, BSc (Hons)
Next generation sequencing (NGS), often referred to as massively parallel sequencing or deep sequencing, refers to a DNA sequencing technology that enables sequencing of millions of small DNA fragments in unison. This generates a massive pool of data and NGS has revolutionized genomic research studies.
The data created can reach gigabytes in size (the equivalent of 1 billion base pairs of DNA) and using NGS, an entire genome can be sequenced in just one day. By contrast, the previously used Sanger sequencing method, which was used to determine the human genome, took more than ten years to produce the final drafts.
In several ways, discoveries made during the Human Genome Project (HGP) shaped the development of NGS. Reference sequences for the human genome were mainly generated on fluorescent and automated capillary sequencers.
First developed in 1990, capillary sequencing parallelized traditional Sanger sequencing into devices that were able to perform up to 384 reactions simultaneously. The use of radioisotope labels was replaced by fluorescent detection; polyacrylamide slab gels were replaced with polymer-filled capillaries and X-ray film was abandoned in favor of laser fluorescent detection. These developments were made due to the massive sequence capacity that was needed for completion of the human genome.
At the beginning of the twenty-first century, the first drafts of the human genome sequence were completed. Over the following ten years, NGS technologies were developed that could provide high throughput sequencing and produce 20,000 times more data in a single run than the technologies used for the HGP.
Today, sequencing of the HGP era appears low throughput and instead of using numerous capillary sequencers, institutes now run just a few NGS devices instead. The most recent, key article on human genome sequencing that used capillary sequencing was released in 2007 and data that already existed was mainly used. In 2007, more modern technologies started to be used instead.
In 2008, the first paper was published on the production of a human genome sequence (from the DNA of Nobel Laureate James Watson) using NGS. Since then, researchers have published numerous studies of single genomes using a variety of NGS methodologies. More recently, larger scale studies that use NGS for whole genome analysis of patients and families have been performed and the technology has been embraced by cancer experts aiming to characterize tumor types.
In 2015, NGS technologies are now available that enable complete human genomes to be sequenced in just a few days. Coupled to high performance computing and bioinformatics tools for data analysis, individual whole human genome sequences can be created at a cost similar to that of single DNA laboratory tests.