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zymatic reactions. What we need is evidence in this field. Of course, specu- 

 lation is good too. Actual experiments that will show us what a nucleic acid 

 does or what it influences are extremely important to any interpretations we 

 make in this area. 



One thing that I think we can be fairly sure of, is that a nucleotide 

 sequence terminating in an end group can determine to a great extent the spec- 

 ificity of this group of substrates for several enzymes. We know that when this 

 end group is removed from a low molecular weight desoxyribonucleic acid chain 

 the low molecular weight chain may become a substrate for desoxyritonuclease. 

 So the breaks in these sequences may have metabolic significance as well as 

 structural significance. Evidence of this sort is badly needed. 



Running through all of these discussions, of course, has been consid- 

 eration of the transforming principle. I believe that we have exhausted most of 

 the immediate possibilities in this discussion. But I think that one action of 

 radiation upon nucleic acid metabolism has escaped discussion and I think that 

 it may represent one of the most important actions. By this I refer to the work 

 of Lwoff (8) on the induction of lysogeny. 



This area of bacterial physiology and biochemistry is extremely com- 

 plex and I cannot even attempt to make a short rational discussion of it But the 

 phenomena which Lwoff has studied opens up an area of great fundamental im- 

 portance in biology, the phenomon of phage production in a strain of bacteria 

 that has carried the phage, or the ability to produce the phage in a non- infective 

 stage. Lysogeny then is described as the phenomenon of inheritable transmis- 

 sion of host-producing phage. 



Actually this is a thread that has run through microbiology for many 

 years There are many early observations, one of the most interesting being that 

 of DeJong (about 1900) in which it was found that spores of B. megatherium , 

 heated to 100 degrees, were lysogenic. That is when the spores grew out, they 

 produced a phage which caused lysis and death of the organism. 



The modern counterpart of this experiment has been performed by 

 Lwoff and his co-workers. Strains which are susceptible, that is, which are 

 known to carry the genetic characteristics that will permit the development of 

 phage, become lysogenic upon X irradiation or exposure to ultraviolet light. 

 Desoxynucleic acid synthesis and phage synthesis increase so that X radiation 

 actually is an agent that has re-orientated the metabolism of the nucleic acid. 

 The net effect is actually to induce a burst of nucleic acid synthesis. A phenom- 

 enon of this nature, I believe, is just as important as any inhibition of nucleic 

 acid metabolism that can be produced. 



As a contribution to fundamental biology I think it is of infinitely great- 

 er importance. It strikes very close to some of the basic problems: the nature 

 of virus, the production of neoplasia, and the relation that neoplasia may have 

 to an abnormal particle metabolism of this nature. I think this is an area that 

 should be investigated extensively by the radiobiologists. 



Sol, you are working in this field. What importance do you place 

 upon it ? 



SPIEGELMAN: Well, I think it is very important. I think, however, 

 that it is not likely that radiation is going to tell us what it is all about. 



CARTER: Radiation is an inducing mechanism. We have been talking 



