66 MUTATIONS 



different types of changes which fit your definition, Dr. Benzer, we 

 should separate them from one another. 



Freese: I think we cannot really split them. In bacteria, for example, 

 we really don't know in many cases what kind of mutations we have, 

 according to your definition. 



Stern: In certain cases you can and in others, you can't. 



Freese: Yes, so the word, "mutation," is then a general one, and we 

 can use, in addition to this, a further subclassification. 



Auerbach: But I think in many bacteria one can determine by 

 recombination or transformation or transduction whether a mutation 

 is chromosomal or genie. 



Freese: But there are some bacteria which cannot be transduced or 

 which you cannot cross as yet, and, actually, this is the majority 

 of them. 



Lederberg: I think we've reached the status of information about 

 the importance of nucleic acid that, while all of us want to have 

 lurking in the backs of our minds some reservations about the extent 

 of the validity of our proofs, it's just nonsense for us to waste our 

 time in casuistic arguments about whether we have proven that this, 

 that, and every other case of a genetic change has involved nucleic 

 information. Why don't we get down to brass tacks? Most of what 

 we're going to talk about in the next couple of days is going to be 

 changes in nucleic information. There are a few areas where we 

 don't know this for sure, and we can question that point. 



Demerec: If you feel that discussion about terminology or definition 

 has been carried far enough, I would like to ask a very specific ques- 

 tion, which will probably be easier to answer than to define a term 

 like "gene." That question is this: Is there any evidence of the 

 existence or nonexistence of specificity in forward mutations? 



Auerbach: The phage work. 



Demerec: Oh, no, those are all in reverse! 



Auerbach: No, you have them in both directions; the r II. 



Benzer: There is fantastic specificity in both directions. 



Demerec: What is the evidence? 



Benzer: In r II, the A cistron has twice the mutability of the B 

 cistron. 



Demerec: Twice as frequent? 



Benzer: Yes. 



Auerbach: But is it twice as long, then? 



Benzer: It is also twice as long, approximately. 



Auerbach: But that is not specificity. 



