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Circulating-Tumor-DNA-Sequencing (1)

DNA Sequencing is the analysis of specific base sequences. The rapid sequencing method greatly promotes the development of biological science and medical science. It plays an important role in basic biology research, and many other fields such as diagnostics, biotechnology, forensic biology and biosystematics. Since the first time Walter Gilbert found chemical degradation method and Frederick Sanger found “dideoxy” chain-termination method, which also known as “ Sanger method”, the DNA Sequencing technology has gone through several-decade enormous changes. Here I would like to look back into the past and give a brief introduction to the history of DNA sequencing. This is the first part of the development of DNA sequencing in 20th century.

The emergence of sequencing on DNA is a little late. In 1975 Sanger and Coulson published “Plus and Minus” technique, which is a sequencing using DNA polymerase with radiolabelled nucleotides. Clearly he did not think this is efficiently, so he announced the “dideoxy” chain-termination method in 1977, also well-known as “ Sanger method”. This is more rapidly and accurate. At the same time, Maxam and Gilbert published their chemical degradation method. This method avoids the process of enzyme catalysis, as well as the error produced in this process. At the first time, Gilbert’s method is more popular for this reason. But because of the complicated procedure, it was gradually replaced by Sanger method.

Sanger,1958

But Sanger never end his journey of exploration of DNA Sequencing. In 1980, He introduced shotgun sequencing. From this time, some viral genomes were gradually founded such as cytomegalovirus genome and smallpox genome.
In 1982, Akiyosh Wada and Hitachi company made a robot which can read genes by sanger method. It is also a great achivement that combines computer technology with biotechnology.

The first real DNA Seuquencer for business was introduced in 1986 by Applied Biosystems, named ABI Prism 370A, with an output of 1000 bases per day. And it started a new beginning of sequecning company.

A big project was activated in 1990, called Human Genome Project. This was first proposed by American Scientist and officially launched in 1990. It was a project participated by Scientist form China, the United Kindom, Germany, Japanese and the United States. It was finished in 2006. This project is to sequence the whole sequences of nucleotides of human, and draw up the gene map.

In 1998, pyrosequencing was founded. Compared with Sanger method, it do not need electrophoresis, and user-friendly conrol.

Conclusion
The 20th century is a stage for the development of DNA Sequencing technology. In this period, scientist found their way of sequencing DNA and started to make it more effective. And this provided a foundation for the rapid development of DNA sequencing technology in the 21st century.

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