History of DNA research

Further information: History of molecular biology

DNA was first isolated by the Swiss physician Friedrich Miescher who, in 1869, discovered a microscopic substance in the pus of discarded surgical bandages. As it resided in the nuclei of cells, he called it "nuclein".^[117] In 1919 this discovery was followed by Phoebus Levene's identification of the base, sugar and phosphate nucleotide unit.^[118] Levene suggested that DNA consisted of a string of nucleotide units linked together through the phosphate groups. However, Levene thought the chain was short and the bases repeated in a fixed order. In 1937 William Astbury produced the first X-ray diffraction patterns that showed that DNA had a regular structure.^[119]

In 1928, Frederick Griffith discovered that traits of the "smooth" form of the Pneumococcus could be transferred to the "rough" form of the same bacteria by mixing killed "smooth" bacteria with the live "rough" form.^[120] This system provided the first clear suggestion that DNA carried genetic information, when Oswald Avery, along with coworkers Colin MacLeod and Maclyn McCarty, identified DNA as the transforming principle in 1943.^[121] DNA's role in heredity was confirmed in 1952, when Alfred Hershey and Martha Chase in the Hershey-Chase experiment showed that DNA is the genetic material of the T2 phage.^[122]

In 1953, based on X-ray diffraction images^[123] taken by Rosalind Franklin and the information that the bases were paired, James D. Watson and Francis Crick suggested^[123] what is now accepted as the first accurate model of DNA structure in the journal Nature.^[5] Experimental evidence for Watson and Crick's model were published in a series of five articles in the same issue of Nature.^[124] Of these, Franklin and Raymond Gosling's paper was the first publication of X-ray diffraction data that supported the Watson and Crick model,^[125][126] this issue also contained an article on DNA structure by Maurice Wilkins and his colleagues.^[127] In 1962, after Franklin's death, Watson, Crick, and Wilkins jointly received the Nobel Prize in Physiology or Medicine.^[128] However, debate continues on who should receive credit for the discovery, as the Watson and Crick article in Nature was based on Franklin's data without either acknowledgment or her knowledge.^[129]

In an influential presentation in 1957, Crick laid out the "Central Dogma" of molecular biology, which foretold the relationship between DNA, RNA, and proteins, and articulated the "adaptor hypothesis".^[130] Final confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 through the Meselson-Stahl experiment.^[131] Further work by Crick and coworkers showed that the genetic code was based on non-overlapping triplets of bases, called codons, allowing Har Gobind Khorana, Robert W. Holley and Marshall Warren Nirenberg to decipher the genetic code.^[132] These findings represent the birth of molecular biology.

http://en.wikipedia.org/wiki/DNA