Reflections on an accidental discovery
In the spring of 1968, my small research group on the Berkeley campus of the University of California was abuzz. Nearly two years had passed since my arrival as an assistant professor of chemistry. The country in general, and Berkeley in particular, was under the dark shadow of the Vietnam War. There were frequent demonstrations on campus, and once the campus was teargassed by a helicopter. For weeks a “stink bomb” left a repugnant smell in our elevator, and one day a band of demonstrators snaked through the chemistry buildings to look for “military lasers” that never existed. One of my graduate students, who had published with me a year earlier the first report on the formation of DNA catenanes (Wang and Schwartz, 1967), was quitting science to do something he considered more relevant. A second graduate student was having a tough time in his work on a DNA sequencing strategy. He and I were trying to take advantage of a report five years earlier that the enzyme E. coli DNA polymerase I could incorporate a ribonucleotide into its product under certain conditions. This misincorporation of a ribo- rather the normal deoxyribonucleotide, I reasoned, might be exploited to generate a set of four copies of a particular DNA template, each with an occasional ribonucleotide substitution rA, rU, rG, or rC at a random position in the DNA chain. Because the presence of a ribonucleotide in a DNA strand would make the backbone sensitive to alkali hydrolysis at that point, alkali treatment of the set of four products would be expected to yield four sets of DNA chains, each ending in a particular nucleotide—a nice set for determining how the four corresponding DNA nucleotides were arranged in the original DNA template.
KeywordsHelical Structure Accidental Discovery Negative Supercoils Covalent Closure Positive Supercoils
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- Wang, J.C. and Liu, LF., 1979, DNA topoisomerases: Enzymes that catalyze the concerted breaking and rejoining of DNA backbone bonds.” InMolecular Genetics, Part III (J.H. Taylor, ed.) Academic Press, New York. pp. 65-88.Google Scholar