462 RADIATION BIOLOGY 



this field, or to other fungi and to bacteria by numerous other workers. 

 Until now, the methods used by them for detecting "biochemical 

 mutants" have focused attention chiefly on gene changes which affect the 

 ability of the given organisms (which are in most respects "autotrophic") 

 to synthesize those organic substances which in most animals must be 

 supplied ready made, such as amino acids, vitamins, purines, and pyrimi- 

 dines. Considerable advances have thereby been made already in trac- 

 ing the complicated courses of synthesis of these materials, despite the 

 fact that the view of each enzyme being the product of one particular 

 gene is proving to have been a serious oversimplification (Bonner, 1952), 

 just as was the view of some early geneticists that all "characters" what- 

 soever of the organism bear a one-to-one relation to their genes. Such an 

 interpretation is entirely unnecessary to the dramatic success which the 

 method has achieved in unraveling biochemical reaction chains and net- 

 works, and not only cell physiology but even organic chemistry proper is 

 falling in debt to this work. 



Even at that, the possibilities of analysis of the metabolic processes 

 common to higher organisms in general — including the holozoic ones — 

 have as yet scarcely been scratched. They await the devising of methods 

 of detecting, preserving despite themselves, and studying the biochemical 

 effects of those still more numerous lethal and detrimental genes which 

 have to do, not with the synthesis of the so-called "food constituents," 

 but with the carrying on of anabolism and catabohsm from that point 

 forward. And beyond these more general and widely distributed bio- 

 chemical reactions, in turn, lie the vast multitude of more special ones 

 which serve in those processes of development, differentiation, and main- 

 tenance whereby each phylum, class, and even species is distinguished 

 from the others. Here the studies of biochemistry, physiology, morpho- 

 genesis, and evolution meet. Here the subtlest tool of genetics — gene 

 mutation — must constitute the major as well as the most delicate instru- 

 ment. And in the provision of these gene mutations will be found the 

 most important contribution which radiation can make in the solution 

 of the problems of the biochemist and the biologist proper, as distin- 

 guished from those of the geneticist himself. 



REFERENCES 



(Information on availability of government reports indicated by an asterisk may be 

 obtained from the Office of Technical Services, Department of Commerce, 



Washington, D.C.) 



Altenburg, E. (19.30) The effect of ultraviolet radiation on mutation. Anat. 



Record, 47: 383. 

 and H. J. Muller (1920). The genetic basis of truncate wing — an inconstant 



and modifiable character in Drosophila. Genetics, 5: 1-59. 

 Anderson, E. G., and L. F. Randolph (1945) Location of the centromeres on the 



linkage maps of maize. Genetics, 30: 518-526. 



