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The discovery of DNA by James Watson and Francis Crick changed everything as it relates to genetics, human growth, disease, treatments, and potential cures. But Watson and Crick's discovery was actually a culmination of events dating back to the late nineteenth century.
The history of DNA research went like this:
- In or about 1899, a German biochemist found that nucleic acids were made of sugar, phosphoric acid, and several nitrogen bases. Later it was found that the sugar can be ribose or deoxyribose, thus RNA and DNA.
- In 1943, Oswald Avery, an American, proved that DNA carried genetic information. He believed DNA might actually be the gene. At the time, most scientists believed the gene would be a protein, not nucleic acid.
- In 1948, Linus Pauling discovered that many proteins take the shape of an alpha helix, like a spring coil.
- In 1950, Erwin Chargaff, a biochemist, found that the nitrogen bases in DNA were arranged in a variance, but the amount of certain bases always occured in a one-to-one ratio. This formed an important foundation for the later description of DNA.
- In or about 1950, research to discover DNA's structure began full bore. At Cambridge University, Francis Crick, a graduate student, and James Watson, a research fellow, were inspired by Pauling's work. At the same time, in London at King's College, Maurice Wilkins and Rosalind Franklin were also studying the structure of DNA. The Cambridge team was making physical models while the King's College team used x-ray diffraction images.
- In 1951, Franklin determined that DNA existed in two forms depending upon the relative humidity in the surrounding air. She deduced that the phosphate part of the molecule was on the outside. Working mostly on her own, Franklin further determined that the "wet" form of DNA had all the characteristics of a helix. She withheld her findings pending more evidence.
- In early 1953, Franklin's partner Maurice Wilkins broke the silence and secretly shared her findings with Watson at the Cambridge facility.
- In later 1953, Watson and Crick took a crucial conceptual step suggesting the molecule was made of two chains of nucleotides, each in a helix as Franklin had found, but one going up and the other going down. Crick believed that matching base pairs interlocked in the middle of the double helix to keep the distance between the chains constant. Watson and Crick showed that each strand of the DNA molecule was a template for the other. They established that, during cell division, the two strands separate and on each strand a new other half is built, just like the one before. This way DNA can reproduce itself without changing its structure -- except for occasional errors, or mutations.
- In 1962, Watson, Crick, and Wilkins won the Nobel Prize for physiology-medicine. Franklin had died by that time and did not share in the glory.
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