STUDIES ON HIGH AND LOW NON-DISJUNCTION 



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llu' y-chromosomc had nothing to do with the pcrcontage of exceptions 

 and also that the autosomes were not responsible for this percentage 

 since hy these crosses the high-percentage producing females should at 

 least in some instances have been heterozygous for the autosomes of 

 the high non-disjunctional stock, lîut in order to have a more exact 

 answer to this point the loilowing experiments were carried out. A 

 numl)er of pair-cultures were raised where the flies had the consti- 

 tution of the high non-disjunctional stock (Table 1). (It must be 

 remem])ered that whereas the crosses in this stock from the beginning 



were of the type j^ X B there had arisen before the beginning of the 



experiments here published two lethals \li and I r] in the forked-bearing 

 chromosome). 



TABLE 1. 



Offspring of cosin exceptional d<mghters from high non-disjunctional 

 cultures when mated by Bar exceptional sons from high non-disjunc- 

 tional cultures. 



Percentage of exceptions 24,(>7 ± 1,16. 



As table 1 shows the result was a total of 1382 flies with 24,67 rt l,i6 

 percent of exceptions. Next (table 2) exceptional females from the 

 high non-disjunctional stock or from table 1 were crossed to males 

 from other sources giving a total of 1995 and an exception-percentage 

 of 21,40 + 0,92. In three different cultures crosses of the same kind 

 were made but with the difference that the males carried in addition 

 to other genes the gene eosin and thus making it impossible to 

 distinguish regular and exceptional daughters. However, among a total 

 of 132 males there were 17,42+3,3 percent of exceptions. (Table 3). 



