James Dewey Watson is a U.S.-born molecular biologist internationally known for having codetermined the double helical structure of the deoxyribonucleic 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 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.
Watson and Crick started their collaboration with the aim of determining the three-dimensional structure of DNA. At that time (1951), biophysicists Maurice Wilkins and Rosalind Franklin at King's College, London, were also investigating DNA and from X-ray evidence had postulated that it might be a helical structure. Linus Pauling at the California Institute of Technology was also looking at DNA after publishing his celebrated alpha helical structure of the protein hemoglobin. It was, therefore, believed that DNA was a helical molecule, but its concrete arrangement remained unclear.
Watson and Crick entered into contact with Wilkins and Franklin and requested a series of X-ray pictures obtained by the latter. From the spot patterns, they deduced the most plausible arrangement of the DNA components with the aid of chemists working in Cambridge and elsewhere. This chemical expertise proved crucial, because it allowed Watson and Crick to test different structures and see which one was more plausible from the viewpoint of the possible chemical bonds between atoms and molecules. Using cardboard-and-brass models similar to jigsaw pieces and children's toys, they came up with the double helix of DNA.
The structure was presented in a paper in Nature dated April 1953. In it, Watson and Crick's main argument for the double helix was the chemical complementarity of the base A with T and of the base G with C. This led the bases to stick together when in contact and allowed one strand of the double helix to hold to the other through linkages between As and Ts and between Gs and Cs, respecting Chargaff's proportions. From the complementarity argument, Watson and Crick postulated a duplication mechanism for DNA in which one strand contained the necessary information to reconstruct the other. This feature, confirmed in subsequent years by the Hershey-Chase and Meselson-Stahl experiments, was raised as evidence that DNA was the genetic material.
Watson left Cambridge shortly after the elucidation of the double helix, and in 1956 he obtained a position in Harvard University. There he worked on the mechanism of the genetic code—how DNA directs the formation of proteins—and in 1968 was appointed director of the Cold Spring Harbor Laboratory on Long Island, New York, a center with a strong tradition of meetings on genetics and DNA. This same year he published The Double Helix, an autobiographical account in which he revealed the competition, ambitions, and rivalries behind the 1953 achievements.
The book was critically received by leading figures in the biomedical community, including Wilkins and Crick, for it described how the Cambridge researchers obtained Franklin's DNA images without her explicit approval. Franklin had died in 1958, a victim of cancer, and she could not share the Nobel Prize, only awarded to scientists before death. Since then, she has been considered the forgotten figure of the double helix and a symbol of discrimination against women in science.
Watson has been involved in further controversies and always liked to act as an iconoclastic scientific authority. In 1988, he was appointed head of the recently approved Human Genome Project, a concerted international effort to determine the base sequence of our DNA. He resigned in 1992 when the U.S. federal administration initially backed the possibility of patenting human DNA sequences. More recently, he was quoted in the media as saying that women should be allowed abortion if unhappy with prenatal genetic testing results and that intelligence is lower in people of color. This latter claim generated considerable public controversy, and in 2007 Watson resigned his position as chancellor of Cold Spring Harbor Laboratory. In the following year he was named chancellor emeritus of the laboratory, where he continues to play an advisory role.
Crick, Francis, Gene, Gene Patenting, Human Genome Project, Mendel, Gregor
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