Special Section: THE CELL: Unraveling the Double Helix and the Secret of Life

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Inspired by these experiments, Watson, then a young Ph.D. in biology from Indiana University, decided to take a crack at the complex structure of DNA itself. The same thought struck Crick, a physicist turned biologist who was preparing for his doctorate at Cambridge. Neither man was particularly well equipped to undertake a task so formidable that it had stymied one of the world's most celebrated chemists, Linus Pauling. Watson, for his part, was deficient in chemistry, crystallography and mathematics. Crick, on the other hand, was almost totally ignorant of genetics. But together, in less than two years of work at Cambridge, these two spirited young scientists showed how it is possible to win a Nobel Prize without really trying.

In 1968 Watson himself produced a highly irreverent, gossipy bestseller, The Double Helix, which revealed the human story behind the discovery of DNA's structure: the bickering, the academic rivalries, even the deceits that were practiced to win the great prize. Out of Pauling's earlier work, Watson and Crick got the idea that the extremely long and complicated DNA molecule might take the shape of a helix, or spiral. From the X-ray crystallography laboratory at King's College in London, where Biochemist Maurice Wilkins was also investigating the molecule's structure, they quietly obtained unpublished X-ray data on DNA. Relying as much on luck as logic, they constructed Tinkertoy-like molecular models out of wire and other metal parts. To everyone's astonishment, they suddenly produced a DNA model that not only satisfied the crystallographic evidence but also conformed to the chemical rules for fitting its many atoms together.

OUT OF THE architecture of their precisely constructed double helix emerged the secret of DNA's awesome powers. The banisters of the staircase were fashioned of long links of sugars and phosphates; the steps between them were made of pairs of chemicals called bases, weakly joined at the center by hydrogen atoms. Only four different bases were used—adenine (A), thymine (T), cytosine (C) and guanine (G). But their sequence could vary so widely along the length of the staircase that they made up an almost limitless information-storage system, like the memory bank of a computer. In addition, because the bases were chemically complementary—that is, A paired off only with T, and C only with G—one side of the staircase was in effect a genetic mirror image of the other. Watson and Crick quickly recognized from the structure of their model how DNA worked. But their 900-word announcement in Nature, the international weekly published in Britain, concluded with one of the more coy statements in scientific literature. "It has not escaped our notice," they said, "that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material."