MAMMALIAN RADIATION GENETICS 151 



D. Uphoff, L. B. Russell, J. W. Gowen, D. Grahn, W. E. Heston, K. Atwood, 

 S. Scheinberg, and certainly many others. 



Techniques developed by mammalian geneticists, originally for genetic purposes, 

 are now finding usefulness in other areas of radiobiology. For example, a group in 

 the Medical Department of the Brookhaven National Laboratory is making extensive 

 use of measurements of survival of spermatogonial cells for detailed analysis of the 

 relative effectiveness of different energy levels of neutron irradiation. 60 ' 1075 This 

 judicious mixture of genetic techniques with those of the medical and radiologic 

 physicist promises to offer much valuable data to the science of radiobiology. 



The geneticist's adherence to quantitative methodology and to sound concepts of 

 the cellular basis of radiation injury have generally assisted in establishing a high 

 standard of scientific accomplishment in the comparatively young and fast-growing 

 field of radiation biology. Geneticists can take pride in their total contribution, 

 direct and indirect, to this scientifically and politically important field of endeavor. 

 Perhaps many remaining problems in radiobiology will ultimately be solved either by 

 geneticists or through genetic techniques and interpretation. 



DISCUSSION 



Dr. Degenhardt: I am very pleased to open the discussion of this excellent paper 

 presented by Dr. Grahn. We are all impressed by the recent advances in this specialized 

 field, but we also recognize that our knowledge is fragmentary in certain areas. On 

 the whole, we have advanced little beyond the first steps into the field of radiation 

 genetics, in which methodologic problems still prevent accurate, rapid, and economic 

 progress. The few well-equipped teams of scientists, who are investigating problems 

 in mammalian radiation genetics, are not sufficient even though their individual efforts 

 are excellent. I should emphasize that it is absolutely necessary (1) to encourage 

 international cooperation and international exchanges of ideas and information in the 

 field of mammalian genetics and (2) to encourage cooperation and exchange of ideas 

 between scientists working with experimental mammals and those working with 

 human beings. This would enable us to collect all information in this field within a 

 reasonable space of time and to estimate better than before the hazard of nuclear 

 damage to human beings. 



After these general comments I should like to direct attention to a certain problem, 

 mentioned by Dr. Grahn: the induction of dominant lethals in germ cells. This is a 

 critical means for examining the areas of physiologic and developmental genetics in 

 early embryonic stages. W. L. Russell, L. B. Russell, and E. F. Oakberg 1142 have 

 demonstrated that the induction of dominant lethals in male germ cells leads to a 

 high incidence of lost conceptus prior to days 10-11 of gestation. Pre-implantation 

 losses rise to about 7 per cent and post-implantation losses to about 25 per cent of the 

 number of corpora lutea at doses below 100 r. 



