When Francis Crick announced in 1953 that he and colleague James Watson had “found the secret of life,” he wasn’t joking. Earlier that morning, the two scientists had decrypted the structure of life’s hereditary information: deoxyribonucleic acid (DNA).

DNA is present in the nucleus of every living cell and guides the cell in making new proteins that determine biological traits. Before Watson and Crick, scientists knew that DNA carried the information that determines all of a living organism’s traits and they assumed that DNA was copied from one generation to the next, but no one knew how this information was encoded or exactly how it was transmitted.

Crick (1916–2004), an English researcher, and Watson (1928–), an American postdoctoral scholar, shared a lab at Cambridge University in the 1950s. Together, they discovered that a strand of DNA looked like a twisted ladder, which they called a double helix. They also realized that each strand was made up of four building blocks, called bases. These building blocks were named adenine, thymine, guanine, and cytosine (also known as A, T, G, and C) and were bound together with hydrogen atoms to create different patterns. Working with cardboard replicas of the four bases, Crick and Watson realized that adenine and thymine always bound together, as did guanine and cytosine. These bonds form what look like rungs on DNA’s twisted ladder. When a cell reproduces, this ladder “unzips,” and new bases are added to each side of the helix—resulting in two new cells with identical DNA.

In 1955, the Spanish-American biochemist Severo Ochoa (1905–1993) was the first person to create, in a lab at New York University School of Medicine, a nucleic acid. He worked with ribonucleic acid (RNA), and shortly thereafter, his UCLA colleague Arthur Kornberg (1918–2007) synthesized DNA. These discoveries paved the way for genetic engineering and provided the basis for many drugs used to treat cancer and viral infections. Unraveling the genetic code depends on knowing the structure of DNA and RNA and their configuration as a double helix. Ochoa and Kornberg shared the Nobel Prize in Physiology or Medicine in 1959, while Watson and Crick were awarded the prize in 1962.

ADDITIONAL FACTS

  1. The dramatic story of James Watson and Francis Crick’s discovery was chronicled in Watson’s book The Double Helix and the movie The Race for the Double Helix.
  2. Adenine and guanine are both made up of double-ringed nitrogen bases, while thymine and cytosine are made of single rings.
  3. The researcher Rosalind Franklin (1920–1958), a close collaborator of Watson and Crick who showed them the first x-ray diffraction pictures of DNA and often critiqued their work, died before the Nobel Prize was awarded.