These lecture notes were likely prepared during Crick's appointment as Visiting Professor of Chemistry at Harvard University from February 1 to June 30, 1959. Note (p.3) Crick's mention of a mimeographed report by the Medical Research Council that gave the unit cell dimension of DNA, essential information for discerning the double-helical structure of DNA and the anti-parallel direction of its two strands. The reference was to the report by the MRC's biophysics committee on its visit to King's College's Biophysics Unit on December 15, 1952, which included a description of Rosalind Franklin's crystallographic DNA work and her determination of the unit cell. Watson and Crick were shown the report by Max Perutz, a member of the visiting committee, without Franklin's knowledge.
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