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 X-pattern in the middle is characteristic of a helical molecule with regular repeats; the broad bands at top and bottom indicate 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 mathematical analysis, indicate whether there are 2, 3, or 4 helices, which requires measurement of the intervals between elements of the X-pattern.
Rosalind Franklin (1920 -
1958), whose grad student Raymond Gosling (1926 - ) made
Photo 51 in May 1952. Maurice
Wilkins (1916 - 2004), working in the same lab group,
with Gosling's assistance had previously made photos of the B
form as early as 1951. Wilkins and Franklin had a severe
personality crash, based in part on their understanding that the
DNA structure problem had been assigned to either of
them, exclusively. Wilkins approached DNA as a
biological problem whereas 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.
Crick, & Wilkins subsequently received the Nobel
Prize in 1962 for solving the structure of DNA.
Wilkins had by then amassed a great deal of additional
crystallographic evidence for the double-helical structure. Franklin
moved on to other crystallographic studies, notably the
structure of Tobacco Mosaic Virus, and by the time of
the award 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
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 (or) Crick and (or) Wilkins ripped off Franklin's work, who was badly treated because she was a woman.
2) If Gosling made Photo 51 while working for Franklin, who "owned it", 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 the base pairing, I wasn't properly acknowledged."