Lecture 01: Discovery of the DNA double helix

1. Lecture 01: Discovery of the DNA double helix

2. Discovery Process

3. The early 1950s, British scientists Wilkins studied the structure of DNA by X-ray diffraction, he realized that DNA is a kind of helical structure. Knowledge Prelude In 1952, American chemist Pauling published a research report on the DNA triplex chain model, this model was called the alpha helix model. In the end of 1951, a female physicist Franklin took a very clear DNA X-ray diffraction photograph. In 1951, Pauling (1954 Nobel Prize winner in Chemistry), found that the protein helix structure of the peptide chain. Already knew the chemical composition of the DNA: the de-oxyribose (J), phosphate (P) and four organic bases: adenine (A), guanine (G), thymine (T) and cytosine (C).

4. A Symposium • In 1952, A symposium in Italy Wilkins, Franklin and Watson are discussed Pauling's model. • Wilkins presented Franklin’s DNA X-ray diffraction photographs captured a year ago. • Watson saw the internal helical structure of DNA, he immediately generated a new concept: the DNA is not a three-chain structure, it should be double-stranded structure. • They continued to follow this thought with depth research in this regard, strongly together.

5. Watson Crick Like-minded • After this time, Watson and his good friend Creek, according to various DNA research information and the results of their own research and come to a consensus: DNA is a double-stranded helix. This is really an exciting discovery! Watson and Crick took action to join in the laboratory immediately began to build a model of the DNA double helix. Started fighting with effect from Feb. 22, 1953, they worked day and night, sleepless nights, and finally on March 7 in the same year, the model of DNA they imagined was built successfully.

6. DNA Double Helix model Nobel Prize Winners James Watson (34y) Francis Crick (46y) Maurice Wilkins (46y) 1953~1962

7. New Era in Life Sciences • Watson and Crick’s model accurately reflect the molecular structure of DNA. Since then, the history of genetics and biology from the cell stage into the molecular stage. • For the outstanding contribution to DNA molecules Watson, Crick and Wilkins share the 1962 Nobel Prize in Physiology and Medicine. • Objectively speaking, due to this epoch-making discovery, the entire life sciences, and the whole of natural science has undergone enormous changes. This is a fact known to the world.

8. The Scholar's Life

9. James Dewey Watson • James Dewey Watson was born on April 6,1928, Chicago. 16-year-old got his bachelor's degree in zoology at the University of Chicago. Engaged in genetic studies by X-ray irradiation of phage, aged 22, obtained his doctor degree, and then to the University of Copenhagen, Denmark, and the University of Cambridge. • Met in the Cambridge University Cavendish Laboratory Creek, become his good friends, by Crick impact, turned to the study of genetic mechanisms, in particular, the structure of DNA. • In the heady days of February 22, 1953 to March 7, they finally built the model of the long-chain molecules of the DNA double helix.

10. James Dewey Watson • Watson proposed the double helix structure of the DNA molecule was only 25 years old, later, he and Crick took further study on the mysteries of the genetic code, the concept of the genetic code. MW Nirenberg (winner of the 1968 Nobel Prize in Physiology) eventually proposed the theory of “triple codon" lay a solid foundation. • 1956 Watson worked at Harvard University, as an Assistant Professor, Associate Professor; 1960 at age 32 became a professor; receiving the Nobel Prize in Physiology in 1962. • In 1962, Watson was elected to be the National Academy of Sciences of the United States, 1977 got Presidential Freedom Award, which is the highest award of the United States.

11. Francis H.C. Crick • June 8, 1916 Francis H.C. Crick was born in Northampton, a UK city, his high school and college education was in London. 21-year-old he got his bachelor's degree in the University of London, then a PhD degree. • In 1939, the World War II outbreak, Crick forced to interrupt their studies, for 8 years to the study in the mines and other military weapons in the British Navy. • The end of the war in 1947, Crick, 31 years old, came to the University of Cambridge, as a biophysical researcher. He convinced that his knowledge of physics to contribute to the study of biology. • In 1950, he again became a doctoral student, 1954, he "X-ray diffraction - peptides and proteins" This paper was awarded the doctorate in biology.

12. Francis H.C. Crick • The friendship with Watson had made a key influence on his molecular biology research career. • Crick and Watson found the double helix of DNA like a zipper, when opened, i.e. the formation of two single-stranded; then as a template for the respective two single-chain, synthesis of complementary single-stranded, thereby generating two identical to the original, the new zipper. This finding is recognized as the most important biological discovery in the 20th century. • In 1958, he and other prominent molecular biologists together determined the "central dogma" of molecular biology. • In 1959 he was elected to be a member of the Royal Society of London; his life was awarded the highest award of the numerous scientific community.

13. Thank you !