1234 



BIOUXilCAL EFFECTS OF RADIATION 



Table 14. — Comparison of Chromosome Aberrations and Point Mutations 



AFTER Treatment of Adult Males and Females 



9 Data of MuUer (Patterson and Muller, 141); d^ Data of Oliver (125) 



spermatocytes or spermatogonia. The differences are of an order of 

 magnitude sufficient to account for the differences in the observed lethal- 

 mutation rate. 



Were this so, the proportion of viable mutations should be constant 

 no matter what stage of development is treated. Earlier experiments of 

 Muller (112) had indicated a higher proportion of viable mutations from 

 mature spermatozoa (Table 15). However, the more extensive experi- 

 ments of Timofeeff-Ressovsky (Table 16), of Hanson and Winkelman 

 (Table 17), and particularly of Moore (Table 18), show only slight 

 differences in the proportion of visible mutations obtained either in the 

 two sexes or in the different age groups. It is conceivable that, as 

 Muller has suggested, the difference is due to a difference in rate of 

 division of mutant and germ cell. Since, however, in none of the pub- 



Table 15. — Comparison of the Frequency of Viable Mutations in Males, 



Treated as Adults and as Larvae 

 X-ray treatment. (Muller, 112) 



Table 16. — The Frequency of Viable Mutations from Germ Cells of Different 



Stages 

 cf" d^ X-rayod and mated at intervals of five days to fresh virgin 9 9 . (Timof<5efT- 



Ressovsky, 178) 



