INDUCED CHROMOSOMAL ABERRATIONS IN ANIMALS 1178 



chromosome) were irradiated and crossed to females homozygous for the 

 fourth chromosome recessive eyeless (ey). Bl D males were selected 

 in Fi, and back-crossed to homozygous ey females. The offspring of 



X-Rotys 

 ah A J'B 



ab Ab otB 



Duplication, Deficiency, 

 dies dies 



Fig. 1. — Scheme of the detection of a translocation. Genes A and B behave normally 

 independently since they are located in different chromosomes (one of which is represented 

 black and the other stippled). In individuals carrying a translocation involving these 

 chromosomes the genes .4 and B exhibit linkage, since gametes Ab and aB produce no viable 



zygotes. 



such a back-cross should consist of 16 equally frequent classes shown in 

 Table 1. Among 121 males tested, 112 actually gave this result. But 

 9 males gave aberrant results. 



The first four cultures shown in Table 1 show no recombinations for 

 Bl and D; here translocations involving the second and the third chromo- 

 somes were induced. The remaining five cultures fail to show recombina- 

 tions for D and ey. Here we are dealing with translocations between the 

 third and the fourth chromosomes. 



