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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    5'- Phosphote Phosphate- Hydrogen Phosphate - deoxyribose -bonded deoxynbose backbone base pairs backbone Figure 1.2: Two dimentional projection of the hydrogen bonded anti- parallel chains of a double helix. Negative charges would usually be neutralised by counter-ions. Projection not to scale pyrimidines. As figure 1.2 shows, these interactions are specific, for guanine can form three hydrogen bonds with cytosine and adenine can form two hydrogen bonds with thymine; these are the complementary base pairs. The specificity of their formation explains the equality found in the base composition of DNA; the number of adenine residues is always the same as the number of thymines and the number of guanines equals the number of cytosines (reviewed by Chargaff, 1971).