MUTAGENS OF POTENTIAL SIGNIFICANCE 227 



Russell: Yes. 



AtiDood: So that that would be a very good test. It would include 

 a lot of the genetic material. 



Lederberg: What is the dose rate dependence on lethals? 



Russell: Dose rate dependence? We have tested this and found 

 no dose rate effect for dominant lethals in postspermatogonial stages. 



Novick: Is it linear with total dose? 



Russell: Yes, as far as we can tell. 



Magni: There is another possibility of directly testing the effect of 

 caffeine. As you know, there are a few people who have tried to 

 estimate the true average mutation rate in man, by different ways, 

 from demographic data. Going back to the system that Cavalli tried 

 to use, it should be just a question of asking another question in a 

 demographic questionnaire: "How many cups of coffee did your 

 father drink?" 



Lederberg: Does everybody here know the system that Dr. Magni 

 is talking about? 



Magni: I think I mentioned it previously. I don't know whether 

 it would be worth while to recall it. 



Neel: Please do. 



Magni: Yes. Cavalli (13) is analyzing statistically a very simple 

 fact. He is taking into consideration the sex ratio of the progeny of 

 women and correlating it with the age of their father at the time of 

 their birth, in order to see if recessive lethals accumulate in gametes 

 with increasing age. 



Atwood: Sex-linked? 



Magni: Yes, sex-linked recessive lethals. This has been done so far 

 on a sample of 60,000 married women. The regression of the ratio 

 males/females born alive to the woman, on the age of the woman's 

 father at the time of the woman's birth has a negative slope, as 

 expected, though not significantly different from zero; the same ratio 

 among the stillborn has a positive slope (which is significantly dif- 

 ferent from zero) , as expected. 



At the moment, data are being collected from birth registrations, 

 and at the end of 1960 there should be some 800,000 births available. 

 I don't know, however, if it will be possible to have questions on coffee 

 consumption added to the Italian census. 



Goldstein: It might be worth pointing out, apart from the general 

 heterogeneity of the population with respect to caffeine exposure, there 

 are certain special groups within the population who do not expose 

 themselves to caffeine, for example, the Seventh Day Adventists or 



