Genetic 342 A&B Kenneth G Wilson Professory of Botany

Data in is like hind-sight it is 20:20 it is what is known at the time

Evidence known and used by Watson and Crick in 1953 to construct a model of DNA

• In 1868 Friedrick Miescher first studied nuclein or nucleic acid.
• In 1910 Phoebus A. Levene proposed the tetranucleotide hypothesis.: A = C = G = T.
• Base Composition Studies
• Between 1949-53 Erwin Chargaff developed some rules for DNA - A=T, C=G, Purines + Pyrimidines etc.
• Between 1938-47 William Atsbury determines a 3.4 Angstrom periodicity
• Between 1950-53 Rosalind Franklin and Maurice Wilkins verify Atsbury and suggest a helix of some type.
• Thus, X-Ray Diffraction Analysis gives evidence that the unit cell is about 20 by 34 Angstroms with repeats at 3.4 Angstroms and that there is some type of helix.
• Proteins have an alpha helix structure as proposed by Linus Pauling.
• The chemical structure of the Sugars and the Bases
   

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