In a Cambridge laboratory, James Watson pieced together cardboard cutouts of nucleotide bases and noticed adenine paired neatly with thymine, guanine with cytosine. The insight explained how DNA could replicate itself and unlocked the double helix structure, which he and Francis Crick would publish weeks later. It became one of the twentieth century's defining scientific breakthroughs.
James Watson later wrote that on the morning of February 28, 1953, he arranged cardboard models of DNA's four bases on his desk at the Cavendish Laboratory and suddenly saw that adenine could pair with thymine, and guanine with cytosine, forming identical-shaped rungs regardless of sequence. The realization meant the molecule's two strands were complementary, each capable of serving as a template for the other during replication.
He rushed to tell Francis Crick, who instantly grasped the implication: this was the mechanism of heredity itself, hiding in plain geometric sight. They famously walked into The Eagle pub that lunchtime, where Crick, never one for modesty, announced they had discovered the secret of life.
The pair published their one-page paper in Nature on April 25, 1953, crediting unpublished data from Rosalind Franklin and Maurice Wilkins that had proven crucial to solving the structure. Franklin's X-ray diffraction images, especially the famous Photograph 51, gave Watson and Crick the measurements they needed. She died in 1958 without a Nobel Prize; Watson, Crick, and Wilkins shared the 1962 award.
Key people: James Watson, Francis Crick, Rosalind Franklin