142 MUTATION AND PLANT BREEDING 



92. Vogt, M. 1948. Mutationsauslosung bei Drosophila durch Athyl- 



urethan. Experienta, 4: 68-69. 



93. Wolff, S., and Luippold, H. E. 1955. Metabolism and chromosome- 



break rejoining. Science, 122: 231-232. 



94. — , Atwood, K. C, Randolph, M. L., and Luippold, H. E. 

 1958. Factors limiting the number of radiation-induced chro- 

 mosome exchanges. Jour. Biophys. Biochem. CytoJ., 4: 365-372. 



Comments 



Ross: Is there any evidence lor chemical specificity either for chromo- 

 some breaks or gene mutations at the same locus of both homologues 

 of a chromosome in one cell? 



Auerbach: This is a possibility that interests me very much. I hope that 

 it will be tried this year in our Institute by Doctor Oster who has 

 worked out a scheme for testing it in Drosophila. 



Nilan: Results obtained at Pullman with diethyl sulfate have some 

 bearing on Doctor Auerbach's discussion of the delayed effect of cer- 

 tain chemical mutagens on chromosomes. In barley, very high fre- 

 quencies of chlorophyll-deficient seedling mutations were induced by 

 this chemical. However, only a very few chromosome aberrations were 

 found. Such aberrations, resulting from chromosome interchanges, are 

 common following irradiation. On further study, some evidence for 

 an appreciable frequency of inversions has been obtained. Thus, it 

 appears that more intrachromosomal than interchromosomal rearrange- 

 ments have occurred, indicating a delayed effect of this chemical on 

 chromosomes. 



Caldecott: In regard to the relation between chemical mutagens and 

 ionizing radiations, I would like to re-emphasize the importance of the 

 physiological state of the cell and the kinds and frequencies of genetic 

 damage that can be detected. Clearly, it would be quite impossible to 

 design an experiment where there could be a precise comparison between 

 mutagens. 



Auerbach: I quite agree; it is too often overlooked that any mutagenic 

 treatment — in particular with a chemical — affects the cell, and some- 

 times the organism as a whole, in addition to acting on the chromo- 

 somes. 



