Session K1: Poster Session II (2:00 pm - 5:00 pm)

2:00 PM–2:00 PM, Tuesday, March 16, 2010
Room: Exhibit CD

Abstract ID: BAPS.2010.MAR.K1.20

Abstract: K1.00020 : How Rosalind Franklin Discovered the Helical Structure of DNA: Experiments in diffraction

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  Heidrun Schmitzer
    (Xavier University)

  Dennis Tierney
    (Xavier University)

  Gregory Braun
    (Xavier University)

Rosalind Franklin, a chemical physicist (1920-1958), used X-Ray diffraction to determine the structure of DNA. In 1953 she described the DNA has a helical structure with a period of 34 A and a radius of 10 A. We suggest experiments of varying equipment and difficulty which enable students to follow in the footsteps of Rosalind Franklin's discovery. To do this we increase the scale; instead of a tiny DNA molecule we examine the diffraction pattern of a helical spring from a ballpoint pen, and instead of X-Rays we use light rays. Students can then apply their experiences with diffraction on a helical spring to R. Franklin's X-Ray diffraction photo, which should be made available to them in original size. They can determine the angle, pitch, and radius of the DNA molecule, just like Rosalind Franklin. Our experiments can be used as demonstration experiments in interdisciplinary history and science lectures, or as lab experiments for undergraduate non science and science majors.

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