A. D. HERSHEY AND MARTHA CHASE 



References 



Delbruck, M., and Bailey, W. T., Jr., 1946, Induced mutations in bacterial viruses. 



Cold Spr. Harb. Symposium Quant. Biol. 11: 33-37. 

 DoERMANN, A. H., 1948a, Intracellular growth of bacteriophage. Yearb. Carneg. Instn. 



47: 176-182. 

 1948b, Lysis and lysis inhibition with Escherichia coli bacteriophage. J. Bact. 55: 



257-276. 

 DoERMANN, A. H., and Dissosway, C. F.-R., 1949, Intracellular growth and genetics of 



bacteriophage. Yearb. Carneg. Instn. 48: 170-176. 

 Hershey, a. D., 1946, Spontaneous mutations in bacterial viruses. Cold Spr. Harb. 



Symposium Quant. Biol. 11: 67-77. 

 1951, Reproduction of bacteriophage. Vllth International Congress for Cell Biology, 



in press. 

 Hershey, A. D., and Davidson, H., 1951, Allelic and non-allelic genes controlling host 



specificity in a bacteriophage. Genetics 36: 667-675. 

 Hershey, A. D., and Rotman, R., 1948, Linkage among genes controlling inhibition of 



lysis in a bacterial virus. Proc. Nat. Acad. Sci., Wash. 34: 253-264. 

 1949. Genetic recombination between host range and plaque type mutants of bacterio- 

 phage in single bacterial cells. Genetics 34: 44-71. 

 LuRiA, S. E., 1945, Mutations of bacterial viruses affecting their host range. Genetics 30: 



84-99. 

 ■ 1950, Bacteriophage: an essay on virus reproduction. Science 111: 507-511. 



DISCUSSION 



ViscoNTi (in reply to a comment by Horowitz) : The excess of parental types 

 in Dr. Hershey's experiments can be eliminated by selecting a class of recombi- 

 nants and scoring inside this class for a third character. Making use of the three 

 markers, rl , h and m, the following cross was made: rl h rri^ X rl'^ h^ m. The 

 yield w^as plated on B, so that no difference could be detected between h and /i"*". 

 Of 1003 plaques observed, 177 were r+ m+, thus giving a recombination value of 

 18 per cent. 128 of such plaques were "fished" and tested by a streaking method 

 on B/2. Of the 128 tested, 63 were h and 65 h^. In another experiment, 92 

 plaques were "fished" and tested by plating a sample on double indicator. 43 

 were h; 47 were /i+; and two were mixed. The two mixed plaques account for the 

 2 per cent of heterozygotes for the locus h. 



192 



