CHROMOSOME BREAKAGE BY DIEPOXIDE AND BY X-RAYS 



A few single chromatid breaks occur, but most of the remaining structural 

 changes are chromatid interchanges, either symmetrical or asymmetrical (in 

 about equal quantity) . A few triradial figures appear with accompanying centric 

 or acentric fragments which may or may not show sister reunion [Figure 3). 





I 





i/\ 



Figure 2 



Approximately one-third of the interchanges are within the same chromo- 

 some, frequently between the two arms [Figure 2). 



With treatment of 30 minutes the proportion of interchanges appears to 

 be considerably higher, the ratio of chromatid interchanges to chromosome 

 breaks rises to 1 -4 as compared with 0-47 for the lower dose [Table I and 

 Figure 1). This is at variance with the results with Vicia where Revell^''^ 



268 



