Franklin's X-Ray Crystallography
Refractions & Reflections on the Nature of Science
Regular substances like crystals diffract X-rays in characteristic patterns according to their physical structure. The X-ray crystallograph at right ("Photo 51") shows an exceptionally clear diffraction pattern of a crystallized DNA molecule. The cross pattern in the middle is characteristic of a helical molecule with regular repeats; the broad bands at top and bottom give an indication of the periodicity of the repeats. The photograph is of the highly hydrated B form of DNA, rather than the drier A form, which does not show a distinct helical structure. The photo does not, without analysis, indicate whether there are 2, 3, or 4 helices.
Rosalind Franklin (1920 -
1958), whose grad student Raymond Gosling (1926 - ) made
the photograph in May 1952, worked as a post-doctoral researcher
in the same lab group as Maurice
Wilkins (1916 - 2004). Wilkins with Gosling's
assistance had made photos of the B form in 1951.
Franklin approached DNA as a physical problem in
crystalline structure of the A form. Opinion and
evidence vary as to how and when she interpreted her evidence a
bearing on the helical form of the molecule.
& Wilkins subsequently received the Nobel Prize in
1962 for solving the structure of DNA. Wilkins had
amassed a great deal of additional crystallographic evidence for
the double-helical structure. By the time of the award, Franklin
was dead: the Nobel is not awarded posthumously, nor to more
than three persons. Watson's autobiographic account of the
discovery of "The Double Helix"
(1968) paints an unflattering personal portrait of Franklin, and
has been widely criticized as inaccurate and sexist. Watson and
Crick repeatedly acknowledged that they could not have solved
the structure without the crystallographic evidence
Priority of discovery, acknowledgement of ideas, and ownership
of data continue to be controversial topics in science. The
story of the discovery of DNA structure is an
exceptionally well-documented one. From the evidence and
statements of participants, consider the following statements
1) Watson and Crick ripped off Franklin's, who was badly treated because she was a woman.
2) Whose property is Photo 51, and who was entitled to see it?
3) "Grad students in those days were treated like serfs."
4) "She was definitely anti-helical."
5) I showed them pairing, I wasn't properly acknowledged