Watson, James Dewey (1928- ), is an American biologist. He shared the 1962 Nobel Prize for physiology or medicine with biologist Francis H. C. Crick and biophysicist Maurice H. F. Wilkins, both of Britain. In 1953, Watson and Crick, relying mainly on experimental data provided by Wilkins, devised a model of the molecular structure of deoxyribonucleic acid (DNA). DNA is the substance that makes up genes, the material in cells that determines the characteristics of an organism.

The Watson-Crick model shows that a DNA molecule forms a double helix--that is, it resembles a twisted ladder. Each "rung" consists of one of two pairs of chemicals, called base pairs. If the ladder is divided at the middle of each rung, the legs form two new ladders, each identical to the original ladder. The model thus suggested how genetic information is passed from one generation to the next.

Excerpt from the "Watson, James Dewey" article, The World Book Encyclopedia © 1999