CHAPTER 7 



The Effect of Ultraviolet Radiation on the Genes 

 and Chromosomes of Higher Organisms 



C. P. SWANSON 



The Johns Hopkins University 

 Baltimore, Maryland 



L. J. Stadler 



The University of Missouri and U.S. Department of Agriculture 



Columbia, Missouri^ 



Introduction. Experimental procedures. Genetic effects of ultraviolet radiation. 

 Direct effects of ultraviolet radiation on chromosomes. Spectral relations. References. 



INTRODUCTION 



This review will be concerned with the effects of ultraviolet radiation 

 on the genes and chromosomes of organisms above the microbiological 

 level. The group of organisms thus included is relatively small in num- 

 bers, and the literature is scanty in comparison to that devoted to radia- 

 tion studies on the fungi, bacteria, and viruses. But cytogenetic studies 

 can be made only on organisms with suitable chromosomes. The ultra- 

 violet results obtained with Drosophila 7nelanogaster and Zea mays may be 

 evaluated against an extensive background of X-ray data bearing on 

 problems of cytogenetic interest. Supplementing the data from these 

 organisms are those from Antirrhinum and Sphaerocarpus, which relate 

 to the genetic effectiveness of various wave lengths within the ultra- 

 violet spectrum, and those from Tradescantia and Gasteria, which deal 

 only with induced chromosomal aberrations. 



Each of these species possesses certain disadvantages, none being 

 wholly satisfactory as a test organism because of difficulties of radiation 

 penetration, accurate dosage measurements at the site of genetic altera- 

 tion, or critical analysis of induced effects. Despite these shortcomings, 

 however, the accumulated evidence from ultraviolet studies has been 



1 Cooperative investigations of the Division of Cereal Crops and Diseases, Bureau of 

 Plant Industry, U.S. Department of Agriculture, and Department of Field Crops, 

 University of Missouri. Missouri Agricultural Experiment Station Journal Series 

 No. 1470. 



249 



