GENE MUTATIONS 



live as adults. The effects of such, factors 

 are visible but completely lethal. 



LETHAL NAKED PUPAE, np (pupae). A single fe- 

 male in a pure culture proved heterozygous for 

 this factor. It caused metamorphosis of larvae 

 into undersized naked pupae which attained ap- 

 proximately normal coloration, but died before 

 reaching maturity. This factor (P. W. Whiting, 

 1921f) proved to be linked with orange (P. W. 

 Whiting, 1932a). 



INVIABLE PUPAE, ip (pupae). The following ex- 

 amples will serve to illustrate some of the 

 types of pupae differing in size and bodily 

 proportions and dying on account of lethal or 

 semi-lethal genetic factors (P. W. Whiting, 

 1934b). 



Records of mutant type males segregating 

 from heterozygous mothers not infrequently show 

 more or less numerical deficiency either of 

 wild-type or of the mutant type. When this is 

 statistically significant it is taken to indi- 

 cate the presence of a linked lethal. Usually 

 no record is made of inviable eggs or larvae, 

 but in some cases dead pupae are recorded. The 

 first case of linkage in Habrobracon was found 

 (P. W. Whiting, 1921f) between orange eyes and 

 a factor, lethal naked pupae, having a lethal 

 effect during the pupal stage. Crossovers were 

 19.5 per cent and there were 142 pupae to 160 

 adults indicating that relatively few of the 

 inviables died before pupation. No record was 

 kept of eggs or larvae. The inviable pupae 

 were of approximately normal proportions, per- 

 haps slightly more slender, but they failed to 



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