Notched-winged  females  of  this
   X-linked dominant mutation survive only as a heterozygote.

   The  closely  linked recessive white-eye, facet-eye, and split-bristle
   mutant alleles exhibit the mutant phenotype in these heterozygotes.

   This  is  explained  by  pseudodominance:  the  genes for these 3 loci
   resided on a deletion, together with theN gene.

   Such individuals are partially hemizygous.