Conclusions
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1.
A method for obtaining thymineless mutants is described; it is based on the selective growth of bacteria in medium containing high concentrations of aminopterin and thymidine.
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2.
The forces which allow the appearance of thethy − mutants seem to be spontaneous mutation and selection. The selective agent forthy − mutants is aminopterin, which depresses the growth rate of thethy + cells but not that of thethy − bacteria in the presence of thymidine.
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3.
Thy − mutants can be obtained from various derivatives ofE. coli 15 and K 12.
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We dedicate this paper to ProfessorL. C. Dunn, who retires at the end of this academic year after 34 years of service to Columbia University, with the wish that the will long continue his contributions to genetics.
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This work was supported in part by grants from the American Cancer Society, the National Science Foundation, and the United States Public Health Service.
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Okada, T., Yanagisawa, K. & Ryan, F.J. A method for securing thymineless mutants from strains ofE. coli . Zeitschrift für Vererbungslehre 92, 403–412 (1961). https://doi.org/10.1007/BF00890061
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DOI: https://doi.org/10.1007/BF00890061