330 GENE MUTATIONS CAUSED BY RADIATION 



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DISCUSSION 



Latarjet : 



(1) It seems to me that the "daughter" conception of spontaneous gene mu- 

 tations could find some support in the clonal distribution of host range spon- 

 taneous mutation in bacteriophage among individual bursts, as has been recently 

 shown by Hershey and by Luria. I should like to ask Muller's opinion on this 

 point. 



(2) I don't think that Novick and Szilard's experiments give evidence for a 

 linear relation between dose and ultraviolet-induced mutations in bacteria. 

 These authors repeated the experiments that Demerec and I did previously,* 

 but their main concern dealt with photorecovery. Their dose-effect curves, 

 drawn with few points, fit our delayed-effect curve in the sense of a non-linear 

 relation (their linearity is due to log plotting). I don't think that the mutation 

 from sensitivity to phage resistance may yet be interpreted in terms of a simple 

 gene change. 



* Cold Spring Harbor Symposia Quant. Biol., 11: 38, 1946. 



