Tracy Morton Sonneborn, 19 October 1905 - 26 January 1981

Abstract

The explosive development of genetics and molecular biology that we are now witnessing had its origin, some 40 years ago, in the introduction into genetic research of microorganisms. Compared with the higher animals and plants which had been used previously— Drosophila , maize, mice, etc.— microorganisms had many technical advantages, and as everyone knows, since then genetics has advanced prodigiously. Moreover, in spite of the extraordinary complexity of modern molecular biology, one thing stands out: basically the same genetic principles apply to the whole range of living things, from viruses to man. Everywhere the nuclear elements —ultimately DNA—play an overwhelmingly important role. The microorganisms first used in genetic research were a fungus— Neurospora ,a bacterium— Escherichia coli , and the bacteriophages of E. coli . However, long before these were used, another group of microorganisms—the protozoa—had been considered as potentially suitable. They were unicellular, and unlike bacteria, often had a regular sexual cycle. H. S. Jennings tried for many years to do genetics with the ciliate Paramecium but had little success, owing to difficulties in making controlled hybridizations between genetically diverse lines—an essential minimum desideratum for classical genetic work. In 1930 Jennings employed a young research assistant, T. M. Sonneborn, for the Paramecium work, and as a result, after 7 years, mating types were discovered in P. aurelia . Thereafter genetics along Mendelian lines with the organism became technically feasible. This was ten years before Lederberg and Tatum demonstrated that genetic recombination could occur in E. coli .