Watson, James D.(1928–)

James Dewey Watson is a U.S.-born molecular biologist internationally known for having codeter-mined the double helical structure of the deoxyri-bonucleic acid (DNA) molecule, found in the nuclei of living cells. This achievement in 1953 is considered crucial in the history of biomedicine, because it began to persuade researchers in this field that DNA is the substance constituting the genetic material of all organisms on earth. It also gradually put DNA at the center of attention in science and society as the molecule directing the development and functioning of the living cell and our bodies. Watson was awarded the Nobel Prize in Medicine in 1962, together with Francis Crick and Maurice Wilkins, who were also involved in the determination of the double helix. He has also been the subject of controversies owing to his autobiographical accounts of the 1953 events and, more recently, his public statements about genes and race.

Watson was born in Chicago and always performed as an extraordinarily gifted student. After completing an undergraduate degree in zoology, he moved to the University of Indiana and started a doctorate study under the supervision of Salvador Luria, who was one of the main members of the “phage group” devoted to genetic research. At the time Watson moved to Indiana (1948), genetics consisted in submitting simple organisms—phage viruses in the case of Luria's group—to radiations and other sources of alterations in their genes. The consequences of such alterations in the organism's behavior and external features were further analyzed. The nature of the genetic material remained unknown at that time, and the most accepted hypothesis was that raised by classical geneticists in the early 20th century, which stated that genes were formed by proteins.

Shortly after finishing his doctoral degree (in 1950), Watson moved to the Cavendish Laboratory in Cambridge, United Kingdom, which hosted an emerging school of investigations into the structure of biological molecules. There he started a cooperation with Francis Crick, who was a physicist applying the technique of X-ray crystallography to proteins. This technique yielded the three-dimensional structure of molecules in crystallized form after the crystals were radiated with X-rays. After crossing the crystal, the X-rays diffracted—that is, altered their trajectory—and formed a pattern of black spots on a photographic plate. It was then possible to postulate a structure for the molecule by calculating the diffraction patterns.

In the early 1950s, researchers from different disciplines were beginning to analyze the structure and properties of DNA. Since the late 19th century, DNA had been known as a mysterious substance located in the nucleus of the cell. During the first decades of the 20th century, it had not interested biologists, who regarded DNA as a rather inactive substance in comparison to proteins, the acknowledged functional molecules involved in all the chemical reactions of the cell. However, in the mid-1940s, Oswald Avery and collaborators at the Rockefeller Institute had raised the first evidence [Page 942]that DNA was the genetic material and the first functional mover of the cell. Erwin Chargaff at Columbia University showed in 1951 that the components of DNA—the chemical bases adenine, cytosine, guanine, and thymine—presented a regular proportion: The number of As was similar to the number of Ts, and the number of Gs close to that of Cs.

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