"The structure of DNA - Coldspringharbor"

Date:: [1953]

Reference:: PP/CRI/H/1/13

Catalogue details

Licence: In copyright

Credit: "The structure of DNA - Coldspringharbor". Source: Wellcome Collection.

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distances arid angles, including Tan der Waal distances, are stereochemical^ acceptable. The essential element of the structure is the manner in which the two chains are held together by hydrogen bonds between the bases. The bases are perpend i ciliar to the fibre axis and joined together in pairs» The pairing arrangement is very specific, and only certain pairs of bases will fit into the structure. The basic reason for this is that we have assumed that the backbone of each polynucleotide chain is in the form of a regular helix. Thus, irrespective of which bases are present, the glucosidic bonds (which join sugar and base) are arranged in a regular manner in space. In particular, any two glucosidic bonds (one from each chain) which are attached to a bonded pair of bases, must always occur at a fixed distance apart due to the regularity of the two backbones to which they are joined. The restait is that one member of a pair of bases must always be a xmrine, and the other a pyrimidine, in order to bridge between the two chains. If a pair consisted of two purines, for example, there would not be room for it; if of two pyrimidines they would too far apart to form hydrogen bonds. In theory a base can exist in a number of tautomeric