Inspired Choices


Looking back over the past 150 years of biological research (especially genetics), it is clear that success has fiequently been contingent on the choice of the experimental system. Mendel's breeding experiments with pea (Pisum) plants, which defined the early science of genetics, are rarely acknowledged as setfing that precedent. His choice of peas, although not original Darwmin and others before him had bred garden peas-was key to his success. With peas, Mendel could control poination and develop highly inbred varieties that bred true and had clearly defned, easily observable traits (phenotypes). The importance of the right choice of organism is highlighted by Mendel's inability to obtain comparable results with hawkweed plants (Hieracium). This failure was not because the fundamental aws of inheritance he had deduced with pea plants lacked generality. Rather, it was because the results were confounded by a hawkweed peculianty that was discovered only decades later: Seeds often develop from diploid cells without fertilization. The rediscovery of Mendel's work at the turn of the century owed much to plant breeders. An American apostle of mendelism, R. A. Emerson at the University of Nebraska, adopted Indian corn (maize) as his experimental organism. Each of the kernels on a com cob is the result of a separate fertilization, making it possible to observe many offspring, thereby enhancing the statistical significance of the data. Using maize, Emerson and E. M. East established the novel idea that "quantitative traits" result from the independent inheritance of several different genes and their alleles, and the consequent effect each has on the others. Thus Emerson, along with the scientific dynasty he founded at Cornell beginning in 1914-including M. Demerec, G. F Sprague, B. McClintock, G. W Beadle, and M. M. Rhoades-contributed to the extension and generalization ofmendelian ideas and to the development of the American com industry. By 1914, Drosophila melanogaster, commonly called the fruit fly, had displaced corn as the more advantageous organism for genetic investigation. Its relatively short reproductive cycle (about 10 days), abundantprogeny (100 to 400 per mating), and the fortuitous property that meiosis in males is not accompanied by the usual exchange of chromosome segrnents, made the results of matings readily interpretable. At Columbia University, T. H. Morgan and his colleagues A. H. Sturtevant, C. B. Bridges, H. J. Muller, and their students had seized on these advantages to initiate one of the most intense periods of discovery in genetics. It had taken them only five years to establish that (i) genes occur in linear arrays along each chromosome, (ii) pains of homologous chromosomes exchange

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@inproceedings{CHOICES2008InspiredC, title={Inspired Choices}, author={INSPIRED CHOICES and George F. Sprague and B. Mcclintock and George Wells Beadle}, year={2008} }