DNA History

James Watson Francis Crick




Working together at the University of Cambridge in England, James Watson, an American scientist, and Francis Crick, a British researcher, made a major scientific breakthrough when they discovered the famous "double helix" -- the structure of DNA, the molecule of life.
In the April 25, 1953, issue of the science journal Nature, Watson and Crick wrote: ""We wish to suggest a structure for the salt of deoxyribose nucleic acid (DNA). This structure has novel features which are of considerable biological interest."
Those modest words were an understatement. Nine years later, in 1962, they received the Nobel Prize for answering one of science's long-pondered mysteries, advancing the emerging field of molecular biology in the process.
Watson and Crick's quest helps illustrate how collaboration, creativity, hard work, and serendipity often conspire on the path to scientific achievement.
A Eureka Moment
Deoxyribonucleic acid (DNA) was first isolated in 1869 by the Swiss scientist Friedrich Miescher. He called the white, slightly acidic chemical that he found in cells "nuclein." By the late 1940s, scientists knew what DNA contained -- phosphate, sugar, and four nitrogen-containing chemical "bases": adenine (A), thymine (T), guanine (G), and cytosine (C). But no one had figured out what the DNA molecule looked like.
In 1953, Linus Pauling, the great American chemist, claimed to have discovered the structure of the DNA molecule, but when Watson saw Pauling's research paper (which had not yet been published) on January 28, 1953, he knew it was wrong. A few days later at King's College in London, Watson was shown an X-ray diffraction photograph (see left) of the DNA crystal taken by scientist Rosalind Franklin.
"The instant I saw the picture, my mouth fell open and my pulse began to race," wrote Watson in his book The Double Helix (1968). The photo convinced him that the DNA molecule must consist of two chains arranged in a paired helix, which resembles a spiral staircase or ladder.
The DNA molecule resembles a spiral staircase or ladder. The sides of the ladder are made up of alternating molecules of phosphate and the sugar deoxyribose, while each rung is composed of a pair of nitrogen-containing chemical bases connected in the middle. DNA has four bases - Adenine, Thymine, Cytosine, and Guanine. These bases always join up with the same partners - A with T, and C with G. Graphic courtesy of http://www.ocean.udel.edu/extreme2004/genomics/www.GenomeNewsNetwork.org/J. Craig Venter Institute.

Watson and Crick set about developing a stick-and-ball model of DNA's possible structure. The sides of the ladder were made up of alternating molecules of phosphate and the sugar deoxyribose, while each rung on the ladder was composed of a pair of nitrogen-containing bases connected in the middle. At first, the scientists were uncertain how DNA's four bases -- A, T, C, and G -- link up with each other. Then thanks to a suggestion from a colleague, they realized that the bases always join up with the same partners - A with T, and C with G.
On March 7, 1953, Watson and Crick finished their model, which reached 6 feet tall. "A Structure for Deoxyribose Nucleic Acid" was published in Nature on April 25, 1953. By the late 1950s, their work had been widely accepted by the scientific community.
In 1962, Watson and Crick received the Nobel Prize for Physiology or Medicine with Maurice Wilkins. He had published important crystallography work relating to DNA at the same time as Watson and Crick. Rosalind Franklin, whose photograph provided "a Eureka moment" for Watson, died in 1958 of cancer. Scientists wonder if she would have been honored with the award as well, had she lived.
New Paths
After their discovery, Watson and Crick stayed in touch, but took different paths in science. Watson joined the faculty of Harvard University in 1955, focusing his research on the role of ribonucleic acid (RNA) in protein synthesis. In 1968, he became director of Cold Spring Harbor Laboratory on Long Island, New York. It conducts research on cancer, plant molecular biology, cell biochemistry, and neuroscience. In 1989, he was appointed director of the National Center for Human Genome Research at the National Institutes of Health and launched a worldwide effort to map and sequence the human genome. In 1994, he became president of Cold Spring Harbor Laboratory.
Crick was made a Fellow of the Royal Society in England in 1959. Working with Sydney Brenner, he sought to "unravel the genetic code" by determining how the sequence of DNA bases would specify the amino acid sequence in proteins. By 1961, they had shown that this translation involves a three-nucleotide code, or codon, which opened the door to new biotechnology research ranging from genetic fingerprinting to screening for inherited diseases. In 1976, Crick joined the Salk Institute for Biological Studies in San Diego, California, where he became involved in studies of neurons and how the brain functions. He served the institute as both a distinguished research scientist and former president. Crick died on July 28, 2004, at the age of 88.