Chemicals and Their Effects 



CHARLOTTE AUERBACH 



Institute of Animal Genetics, 

 Edinburgh, Scotland 



It is now almost exactly 20 years since the first highly effective muta- 

 gens were detected. This symposium provides an opportunity for 

 taking stock of developments in this new field of research. There can 

 be no question of its expansion; an ever-increasing number of chemi- 

 cals has been found to be mutagenic, and there is no reason to expect 

 that this expansion will come to a standstill unless we halt it purposely 

 because we feel that there is no good reason for testing more and more 

 chemicals for mutagenic ability. This is one of the points which, I 

 hope, we shall discuss at this meeting. But let us ask a different ques- 

 tion: To what extent has work on chemical mutagens fulfilled the 

 expectations with which it was started? 



Expectations are largely a personal matter, but I think that the 

 main expectations of mutation workers at that time may be classed 

 under three headings. Chemical mutagens were expected to help 

 elucidate (a) the chemical nature of the genetic material and (b) the 

 relationship between intragenic and intergenic changes, and (c) to 

 open the way for the production of specific types of genetic change. 

 How far have these expectations been fulfilled? 



The Nature of the Genetic Material 



The original, somewhat naive, idea was that by studying the chem- 

 ical group or groups that produce mutations we would learn some- 

 thing about the nature of the other partner in the reaction, the genet- 

 ic material. This, I am afraid, has proved an illusion. We now know 

 that there is not one magic group which confers mutagenic ability on 

 a compound. Instead, vastly different compounds may have mutagenic 

 abilities, and closely related ones may differ in this respect. On the 

 other hand, during these 20 years our knowledge of the chemical 

 nature of the genetic material has advanced spectacularly, but the 

 advance did not come from mutation research. The situation now is 

 almost exactly the reverse of what we expected 20 years ago. Instead 

 of inferring the chemical nature of the gene from the nature of the 



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