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Mammalian Radiation Genetics 



W. L. RUSSELL 



Biology Division 



Oak Ridge National Laboratory 



Oak Ridge, Tennessee 



Introduction 



This symposium is concerned with the basic aspects of radiation ef- 

 fects. When we turn to the genetic effects of radiation in mammals, 

 there are so few aspects on which there is any information that the prob- 

 lem of sorting out the fundamental findings has hardly arisen. In this 

 paper it will, therefore, be possible to survey most of what is known 

 and pass on to a consideration of what is needed next. Since one of 

 the purposes of this symposium is an interchange of views between in- 

 vestigators in different fields, an attempt will be made to avoid technical 

 details. 



Among the practical needs in mammahan radiation genetics is a press- 

 ing one for more data on which to base estimates of the genetic hazards 

 of radiation in man. The present paper will be concerned largely with 

 this problem. Our own work is directed primarily in this direction, our 

 objective being to uncover some of the basic facts in at least one mam- 

 mal — the mouse. Before discussing the experimental work, however, it 

 seems desirable to consider some of the general features of the genetic 

 hazard of radiation. 



Nature of the Genetic Hazard of Radiation 



Among the hazards of exposure to radiation, the genetic effects are 

 of importance because of several unique features. 



1. There is usually no healing of the damage. Some types of damage 

 to the genetic material, for example the breaking of a chromosome, may, 

 under certain conditions, heal. Others, for example "cell lethal" mu- 

 tations, are by their nature prevented from passing on to any descend- 

 ants. However, from effects that are actually hereditary, in the sense 

 of becoming manifest in the next or subsequent generations, the only 

 chance of healing lies in the remote possibility of reverse mutation. 



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