CHAPTER 10 



Radiation-induced Chromosome Aberrations in Tradescantia 1 



Norman H. Giles, Jr. 



Osbom Botanical Laboratory , Yale University, and 

 Biology Division, Oak Ridge National Laboratory 



Introduction. Methods; aberration types and their relationships: General experimental 

 techniques — Types of aberrations — Ratio of symmetrical and asymmetrical exchanges — 

 Distribution of breaks in chromosomes — Distribution of aberration types among nuclei — 

 Spontaneous chromosome aberrations — Time of chromosome division. Variations in 

 radiosensitivity during the nuclear cycle. Quantitative radiation results: The relation of 

 aberration yield to dose — The relation of aberration yield to intensity — The space factor in 

 reunion — Proportion of breaks that undergo restitution — Relative efficiencies of various 

 radiations — Aberration production by absorbed radiosotopes — Aberration production 

 by slow neutrons. Recapitulation. Effects of modifying factors: Centr if ligation; 

 Sonic vibration — Colchicine — Ultraviolet — Infrared — Temperature — Oxygen. Conclu- 

 sions. References. 



INTRODUCTION 



Studies on the effects of ionizing radiation on the chromosomes of 

 species of the spiderwort genus Tradescantia have all appeared since the 

 publication of the volumes edited by Duggar (1936), "Biological Effects 

 of Radiation," and, as a consequence, the present review does not consti- 

 tute in any way a revision and extension of earlier observations presented 

 in these volumes. There have appeared, however, within the past few 

 years a number of more or less complete treatments of the early radiation 

 studies on Tradescantia. In particular, the discussions by Lea (1946) 

 and by Catcheside (1945, 1948) have been quite extensive. Under the 

 circumstances, it does not seem desirable to review in as great detail as 

 would otherwise be necessary the material already covered in these 

 publications. In order to make the present discussion reasonably com- 

 plete, however, an attempt will be made to present the essential details 

 of earlier observations, together with references to selected original 

 papers and review articles on these subjects. In addition, a particular 

 effort will be made to provide a more detailed discussion of recent research 

 in this field, with emphasis on those results which appear to necessitate a 



1 Work at Oak Ridge performed under Contract No. W-7405-eng-26 for the Atomic 

 Energy Commission. 



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