Structure of DNA (Watson and Crick model)
Nucleic acids · Biology
DNA double helix
Interactive 3DThe twisted ladder of life — A–T and G–C base pairs winding 10 per turn.
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Study notes
Rosalind Franklin's Photo 51 — the X-shaped X-ray diffraction image — told Watson and Crick the molecule was a helix; they built the double helix in 1953 without crediting her properly (she died in 1958, two years before the Nobel they shared). Every DNA test today — paternity, forensics, ancestry — reads the base-pairing rules A-T, G-C that their model revealed.