Chapter IV 



GENE MUTATIONS 



Habrobracon juglandis has proved to be ex- 

 cellent material for the study of gene muta- 

 tions which produce visible effects, since the 

 haploid nature of the males prevents recessives 

 from being carried over more than one genera- 

 tion before the mutant individuals appear. Most, 

 mutations occurring in the germ tract of a nor- 

 mal wild-type female will appear in her mutant, 

 sons if her eggs are not fertilized. Should 

 her mutant eggs be fertilized, her daughters 

 that develop from these eggs will produce sons, 

 fifty per cent of which will show the new trait. 

 Recessive mutations occurring in the germ tract 

 of a normal wild-type male will become evident 

 in certain of his grandsons; that is, in half 

 the sons of those daughters which developed 

 from eggs fertilized by sperm bearing the mu- 

 tant gene. Of course, this ratio may be dis- 

 turbed by the lowered viability of the mutant. 

 Several mutations have occurred spontaneously 

 in wild-type stocks. These have involved eye 

 color, shape, and size; body color, shape, and 

 size; wing pattern, shape, size, venation, and 

 position; antennal length, structure, and posi- 

 tion; leg length and structure; foot structure; 

 varying degrees of lethality; and sex, Muta- 



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