1940
		1940
	G. W. Beadle and E. L. Tatum publish their classic study on the biochemical genetics of Neurospora and promulgate the ONE-GENE, ONE-ENZYME theory. K. Mather coins the term polygenes and describes polygenic traits in various organisms.	1941
	S. E. Luria and T. F. Anderson publish the first electron micrographs of bacterial viruses. T2 has a polyhedral body and a tail.	1942
	S. E. Luria and M. Delbrück initiate the field of bacterial genetics when they demonstrate unambiguously that bacteria undergo spontaneous mutation.	1943
	O. T. Avery, C. M. MacLeod, and M. McCarty describe the pneumococcus transforming principle. The fact that it is rich in DNA suggests that DNA and not protein is the hereditary chemical.	1944
	S. E. Luria demonstrates that mutations occur in bacterial viruses.	1945	FDR dies in office. Harry S. Truman becomes thirty-third president of the United States.
	J. Lederberg and E. L. Tatum demonstrate genetic recombination in bacteria. Genetic recombination in bacteriophage is demonstrated by M. Delbrück and W. T. Bailey and by A. D. Hershey. Nobel Prize in Medicine awarded to H. J. Muller for his contributions to radiation genetics James B. Sumner, John H. Northrop, and Wendell M. Stanley share a Nobel Prize in Chemistry for Sumner's discovery that enzymes can be crystallized and for Northrop and Stanley's preparation of enzymes and virus proteins in a pure form.	1946
		1947
	H. J. Muller coins the term dosage compensation. J. Lederberg and N. Zinder, and, independently, B. D. Davis develop the penicillin selection technique for isolating biochemically deficient bacterial mutants.	1948
	A. D. Hershey and R. Rotman demonstrate that genetic recombination occurs in bacteriophage. J. V. Neel provides genetic evidence that the sickle-cell disease is inherited as a simple Mendelian autosomal recessive.	1949
		1950