GENE MUTATIONS 



tions have also been induced through X-radia- 

 tion and temperature variation. 



Variations in eye color were among the first 

 mutations to be observed. A quadruple allelic 

 series of factors affecting eye color was re- 

 ported (A. R. Whiting and Burton, 1926). 



ORANGE, (eyes). The normal wild-type, jet 

 black eyes and dark brov/n ocelli, mutated to 

 orange, in which the ocelli have but a slight 

 trace of pigment while the eyes are orange 

 varying to pink and red. The first appearance 

 of orange (P. W. Whiting, 1921c) was in a sin- 

 gle male found March 27, 1920. Crosses between 

 orange and wild-type gave the first definite 

 .genetic check on the supposition that males, 

 being haploid and from unfertilized eggs, in- 

 herit only from the mother. They also gave the 

 first indication that related parents occasion- 

 ally produce a few sons from fertilized eggs 

 which are diploid and like their sisters in ap- 

 pearance. 



IVORY, oi (eyes). On June 24, 1924, there ap- 

 peared in a fraternity of orange stock, four 

 ivory-eyed males. Ivory has colorless ocelli 

 and compound eyes of a greenish v;hite v/ith oc- 

 casionally a trace of pink. This mutation has 

 proved to be recessive to both wild-type and to 

 orange, forming the third in an allelic series. 



LIGHT-OCELLI, ol (eyes). In January, 1925, 

 there appeared from a cross of ivory female by 

 wild-type male a single female with light ocelli 

 but with the compound eyes black as in wild- 

 type. This mutant proved to be an allele of 



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