"A Structure for DNA"

Date:
[1953]
Reference:
PP/CRI/H/1/11/5
Catalogue details

Licence: In copyright

Credit: "A Structure for DNA". Source: Wellcome Collection.

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    in the most plausible tautomeric forms, (that is with the keto rather than the enol configurations) it is found that only specific pairs of bases can bond together« These pairs are: Adenine (purine) with Thymine (pyrimidine) Guanine (purine) with Cytosine (pyrimidine) In otheee words, if an adenine forms one member of a pair, on either chain, then on these assumptions the other member must be thymine. Similarly for guanine and cyt osine. The sequence of hases on a single chain does not appear to he restricted in any way. However, if only specific pairs of hases can he formed it follows that if the sequence of hases on one chain is given, then the sequence on the other chain is automatically determined. It has been found experimentally^'^ that the ratio of the amounts of adenine to thymine, and the ratio of guanine to cytosine are always very close to unity for D.N.A. It is prohahly impossible to build this structure with a ribose sugar in place of the deoxyribose, as the extra oxygen atom would make too close a van der Waals contact. 5 6 The previously published X-ray data * on D.M.A. are insufficient for a rigorous test of our structure. As far as we can tell it is roughly compatible with the experimental data, but it must be regarded as unproved until it has been checked against more exact results. Some of these are given in the adjoining publications^We were not aware of the details of the results presented there when we devised our structure, which rests mainly though not entirely on published