THE INTERACTION OF GENES: THE EFFECTS 



169 



Fig. 80. Vortex, one of the allelomorphs of the dumpy locus, showing the whorls 

 of bristles from which the gene takes its name. 



(After Bridges and Mohr,) 



Vortex . . 

 Oblique. . 

 Dumpy . . 

 Thoraxate 

 Lopped. . 

 Truncate 

 Normal allele 



+ 



+ 



+ 



The individual effects are usually recessive, so that for instance the 

 compound oblique- thoraxate is phenotypically normal; their allelo- 

 morphism is shown by the fact that they both show some effect in 

 combination with dumpy. In the presence of intensifiers, the more 

 extreme effects become partially dominant. 



10. Dosage in Polyploids and Polysomics 



Phenotypic alterations due to dosage changes are also seen in poly- 

 ploids and polysomics. The changes in homozygous autopolyploids 

 are presumably mainly due to alteration in the balance between the 



