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How did X-ray crystallography contribute to the discovery of DNA’s double-helix structure?

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Diagram of the electromagnetic spectrum showing different types of waves arranged by wavelength and frequency, from gamma rays and X-rays to ultraviolet, visible light, infrared, microwave, TV/FM radio, shortwave radio, AM radio, and longwave radio. — X-ray The relationship of X-rays to other electromagnetic radiation within the electromagnetic spectrum.

X-ray crystallography was instrumental in discovering the structure of DNA by allowing scientists to visualize the molecule's internal arrangement. When a beam of X-rays strikes a crystal, the atoms cause the radiation to scatter, creating an interference pattern that reveals the underlying molecular structure.1

In the early 1950s, Rosalind Franklin and Maurice Wilkins produced high-quality X-ray diffraction images of DNA. Franklin’s work was particularly vital, as she established the density of the molecule and provided clear evidence that it existed in a helical conformation.234

James Watson and Francis Crick utilized these diffraction studies to construct a three-dimensional model. By interpreting the patterns, they were able to propose in 1953 that DNA consists of two intertwined helical strands, a breakthrough that fundamentally transformed our understanding of genetics and molecular biology.23