Editing DNA sequencing (section)

=== Discovery of DNA structure and function ===
Deoxyribonucleic acid ([[DNA]]) was first discovered and isolated by [[Friedrich Miescher]] in 1869, but it remained under-studied for many decades because [[protein]]s, rather than DNA, were thought to hold the genetic blueprint to life. This situation changed after 1944 as a result of some experiments by [[Oswald Avery]], [[Colin Munro MacLeod|Colin MacLeod]], and [[Maclyn McCarty]] demonstrating that purified DNA could change one strain of bacteria into another. This was the first time that DNA was shown capable of transforming the properties of cells.

In 1953, [[James Watson]] and [[Francis Crick]] put forward their [[double-helix]] model of DNA, based on [[X-ray crystallography|crystallized X-ray]] structures being studied by [[Rosalind Franklin]]. According to the model, DNA is composed of two strands of nucleotides coiled around each other, linked together by hydrogen bonds and running in opposite directions. Each strand is composed of four complementary nucleotides – adenine (A), cytosine (C), guanine (G) and thymine (T) – with an A on one strand always paired with T on the other, and C always paired with G. They proposed that such a structure allowed each strand to be used to reconstruct the other, an idea central to the passing on of hereditary information between generations.<ref name="pmid13168976">{{cite journal | vauthors = Watson JD, Crick FH | title = The structure of DNA | journal = Cold Spring Harb. Symp. Quant. Biol. | volume = 18 | pages = 123–31 | year = 1953 | pmid = 13168976 | doi = 10.1101/SQB.1953.018.01.020 }}</ref>
[[File:Frederick Sanger2.jpg|thumb|[[Frederick Sanger]], a pioneer of sequencing. Sanger is one of the few scientists who was awarded two Nobel prizes, one for the [[Protein sequencing|sequencing of proteins]], and the other for the sequencing of DNA.]]
The foundation for sequencing proteins was first laid by the work of [[Frederick Sanger]] who by 1955 had completed the sequence of all the amino acids in [[insulin]], a small protein secreted by the pancreas. This provided the first conclusive evidence that proteins were chemical entities with a specific molecular pattern rather than a random mixture of material suspended in fluid. Sanger's success in sequencing insulin spurred on x-ray crystallographers, including Watson and Crick, who by now were trying to understand how DNA directed the formation of proteins within a cell. Soon after attending a series of lectures given by Frederick Sanger in October 1954, Crick began developing a theory which argued that the arrangement of nucleotides in DNA determined the sequence of amino acids in proteins, which in turn helped determine the function of a protein. He published this theory in 1958.<ref name="whatisbiotechnology.org">{{Cite web|title=The path to DNA sequencing: The life and work of Frederick Sanger|url=http://www.whatisbiotechnology.org/exhibitions/sanger/path|access-date=2023-06-27|website=What is Biotechnology?|language=en|first=L. |last=Marks}}</ref>