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Rich used the same diffraction technique to get an image of a small piece of DNA (six base pairs) in 1979. The image confirmed Watson and Crick's proposed structure—except for one major difference. The photo showed that the helical structure bore a left-handed turn, while Watson and Crick's structure called for a right-handed turn. Rich's image thus threatened the validity of the 20th-century's most celebrated theoretical structure. Rich remembers a telephone conversation he had with Crick after looking over his results. "I told him that the structure was left-handed, and he was silent," he said. "Francis Crick is rarely silent."
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