Intergenic suppression of the black mutation of Drosophila melanogaster.

Five X-linked, recessive alleles were isolated which suppressed both the pupal and adult coloration phenotypes of the black mutation. Electron micrographs of shed puparia revealed that the aberrant sclerotization of the black cuticle is also suppressed. Amino acid analysis indicated that suppression is associated with an increased concentration of beta-alanine, an amino acid known to be deficient in black. The suppressor locus mapped at the tip of the X, to the right of scute, and intragenic complementation was observed among the alleles.