THE DOUBLE HELIX

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.
   

Text iGenetics by Peter J. Russell

This web site is provided for instruction in Botany and Zoology 342

by Kenneth G. Wilson,
Professor of Botany
Miami University
wilsonkg@muohio.edu