140 



CARTER: As a matter of fact, Mellinick isolated something like 30 or 

 50 viruses which man lives with perfectly happily. It is a nice relationship. 

 When the viruses undertaken from man were given to mice, the results were 

 disastrous. So that I don't think we have to confine our speculation too narrow- 

 ly- 



MAZIA: There is a variety of genetic responses that may not be found 

 in higher organisms because higher organisms could not have evolved if they had 

 such sloppy genetics. 



SPIEGELMAN: I doubt very much whether the genetics of microorgan- 

 isms is "sloppier" that that of the higher forms. The ' sloppiness" referred to 

 by Dr. Mazia, is more apparent than real. It stems primarily from the great 

 precision with which one can perform genetic experiments with microorganisms. 

 The microbial geneticist can, and routinely does, deal with 10^ individuals and 

 with hundreds of generations. Further procedures have been evolved that permit 

 him to select easily a particular genotype even though it be present in only 1 out 

 of 10^ individuals. The point is that the range and the precision of the observa- 

 tions which can be performed with microorganisms are several orders of magni- 

 tude above that. 



KAMEN: Do you think that anything in humans suggests that they don't 

 have sloppy genetics? 



SPIEGELMAN: I was the one who raised the voice of caution as a mat- 

 ter of fact. 



KAMEN: We will put that on the record. 



POLLARD: I don't believe that these things have much to do with nu- 

 cleic acid as such. It seems to me that what is important is how nucleic acid is. 

 related to the cell. 



CARTER: I think that nucleic acid metabolism is an expression of one 

 of the most integrated activities of the cell and it is the area that is the most at- 

 tractive to study. 



POTTER: This phenomena may represent chunks of nucleic acid com- 

 ing out of the molecule, may it not. Just as an amino acid can come out of the 

 middle of a polypeptide chain, and an intact polypeptide chain cannot go to pieces 

 because of its hydrogen bonds to other chains, so here you may have disrupted 

 units of nucleic acid backbone which can come and go because the structure as a 

 whole is held together by hydrogen bonds. 



I mention this in connection with Dr. Cohn's statement about a line of 

 reasoning which is drawn from the idea that the phosphate is bonded on each end 

 and, therefore, is in there tighter than anything else. If one includes the hydro- 

 gen bonding then this is no longer so. I think that we have to draw our conclu- 

 sions about what goes in and what comes out in terms of metabolic experiments 

 in which we determine whether certain precursors go in and stay in and other 

 precursors go in and come out. I think only by this metabolic experiment can we 

 get at this question of whether the structure is as simple as pictured in the ab- 

 sence of hydrogen bonds. 



This sort of thing suggests that if you break them out, the whole thing 

 does not go to pieces functionally. So I think those two concepts are closely re- 

 lated. It makes me think that the structure as a whole can carry a certain num- 



