Botany · Ch 8 — Biomolecules
Structure of DNA
Structure of DNA
The structure of DNA was proposed by James Watson and Francis Crick, working at the Cavendish Laboratory in Cambridge, who built a scale model of DNA's double-helical structure. Their model was strongly supported by X-ray crystallographic data produced by Maurice Wilkins, and built on the earlier, first clear crystallographic evidence for a helical structure obtained by Rosalind Franklin (1920-1958) at King's College, London, in the 1950s. Watson, Crick and Wilkins shared the Nobel Prize in 1962 for this discovery. As proposed by Watson and Crick, DNA consists of two helical polynucleotide chains coiled around a shared common axis, forming a right-handed double helix - the most common form of DNA, known as B-DNA, which represents DNA's secondary structure. The two coiled strands are held together by hydrogen bonds between complementary pairs of nitrogenous bases: adenine pairs with thymine via two hydrogen bonds, while guanine pairs with cytosine via three hydrogen bonds. The sugar used …
What this figure shows. The DNA double helix drawn with two antiparallel sugar-phosphate backbones (labelled 5' and 3' at each end) wound around a common axis, complementary base pairs (A-T, G-C) shown as horizontal rungs between them, and the resulting major groove and minor groove labelled on the helix surface; the helix diameter (about 20 angstrom) and rise per turn (ab …