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Photo 51: X-Ray Diffraction & the Discovery of DNA's Double Helix

Rebuild Rosalind Franklin's Photo 51 from first principles: adjust the helical pitch, radius and strand stagger of a 3D double helix and watch its computed X-ray diffraction pattern form the famous X, including the 'missing' 4th layer line that revealed DNA's two-strand structure.

Genetics & Evolution3DAdvanced60 FPS📱 Mobile-adapted⇄ 2D version

Rosalind Franklin's 1952 fibre-diffraction photograph of B-DNA is one of the most consequential single images in the history of science. This simulator builds a real double helix in 3D from adjustable pitch, radius and inter-strand stagger, and computes — from the actual Cochran–Crick–Vand helical diffraction formula, not a picture — the X-ray pattern that structure would cast on a photographic plate. Push the strand stagger away from its historical value of 3/8 of the pitch and watch the faint 4th layer line reappear: that single missing spot in the real Photo 51 was Franklin's own measurement, and it was decisive evidence for a two-strand helix with ten base pairs per turn.

⚙ Under the hood

Rebuild Rosalind Franklin's famous Photo 51 from first principles: adjust the pitch, radius and strand stagger of a 3D double helix and watch the Cochran-Crick-Vand formula compute its X-ray diffraction pattern live, including the historic 'missing' 4th layer line.

DNAX-ray diffractionhistory of sciencegeneticsdouble helixbiophysics

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install