Volume 1

Gene expression / Benjamin Lewin.

  • Lewin, Benjamin.
Date:
1974-1977
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Gene expression / Benjamin Lewin. Source: Wellcome Collection.

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    Figure 1.3: A scale space-filling model of the DNA double helix. By kind permission of Professor M. F. H. Wilkins The planar purine and pyrimidine bases in the interior of the duplex are aligned parallel to each other and the planes of the hetercyclic rings are roughly perpendicular to the axis of the helix. The bases are therefore said to be stacked above each other in this parallel array. As the model of figure 1.3 shows, there is a distance of 3-4Â between each base pair so that ten base pairs make up each complete turn of the helix in 34Â. The duplex has a narrow groove of about 12Â across and a wide groove of about 22À. Although hydro gen bonding to form the complementary base pairs explains the specificity