SEX DETERMINATION 



(P. W. Whiting, 1940c, 1943a). Laboratory stocks 

 have been analyzed for sex factors. Technique 

 consisted in selecting one stock, designating 

 its sex alleles as xa/xb, and introducing into 

 it a recessive gene. If all significantly large 

 fraternities from crosses of recessive females 

 of this stock to dominant males of an unknown 

 stock contained dominant males (diploid), as 

 well as the recessive males (haploid) and domi- 

 nant females (diploid), the PI male stock was 

 considered to have the same sex alleles, xa/xb. 

 If no dominant males (diploid) appeared in any 

 of the fraternities, the PI male stock was re- 

 garded as having different alleles — for example, 

 xc/xd. If only one-half the fraternities in- 

 cluded dominant males, the PI male stock was 

 considered to have one allele in common with 

 xa/xb--for example, xa/xi. Recessive genes were 

 introduced into each nev/ stock as it was ana- 

 lyzed for sex factors, and "tester" stocks .were 

 made up for future use. 



Nine factors are thus far known in the series 

 (xa through xi), and the tester stocks are des- 

 ignated xa/xb, xc/xd, xe/xf, xg/xh, and xa/xi. 

 Evidence of allelism of these sex factors is 

 furnished by the fact that they are all closely 

 linked with the gene, fused. Lack of diploid 

 sons and equality of fused and non-fused daugh- 

 ters from crosses of stocks tentatively desig- 

 nated as having different sex alleles in the x 

 series proves the sex factors to be different, 

 but their linkage with fused indicates their 

 allelism. 



The multiple alleles are regarded as differ- 

 ential chromosome segments which have been built 

 up in the early evolution of the Lymenoptera. 



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