Effects of Preirradiation and Postirradiation Cellular 

 Synthetic Events on Mutation Induction in Bacteria 1 



FELIX L. HAAS, CHARLES O. DOUDNEY, and TSUNEO KADA 2 



The University of Texas M. D. Anderson Hospital and Tumor Institute, 



Houston, Texas 



During the past few years several investigations have made it 

 evident that the processes leading to mutation induction by 

 ultraviolet light (UV) are intimately related to gene replication, 

 which is then followed by the influence of the modified gene in 

 enzyme synthesis. Since these events are primarily biochemical, 

 involving interrelations in the syntheses of deoxyribonucleic acid 

 (DNA) ribonucleic acid (RNA), and protein, it seems reasonable 

 that one can no longer examine such biological phenomena as muta- 

 tion induction and expression without simultaneously studying their 

 biochemical basis. Conversely, mutation induction and mutation 

 expression are endpoints of the biochemical events of DNA replica- 

 tion and genetic control of enzyme synthesis respectively, and they 

 may serve as useful tools in working out the biochemistry of these 

 events. 



This paper is concerned with several theoretical aspects of muta- 

 tion induction which have been investigated by such combined bio- 

 chemical and biological studies. The experimental results also have 

 some implications for modern theories of genetic DNA replication. 

 At the very least, it is hoped that the value and relative ease of 

 performing such integrated studies will be demonstrated. 



The importance of the physiological state of the biological mate- 

 rial used in such investigations, and probably in all biological investi- 

 gations, cannot be overemphasized. It is obvious that the same 

 biochemical and physiological processes are not operating at all 

 times during the life cycle of any cell. Important events may be 

 entirely obscured when working with random populations composed 

 of members of all ages and stages of physiological development. 



ir Lhis investigaton is supported in part by research grant C-3323 from the National 

 Institutes of Health and by Atomic Energy Commission contract AT-(40-l)-2139. 



Postdoctoral Research Fellow; Research Training Grant CRT-5047 from the 

 National Institutes of Health. 



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