PHYSICAL MAP OF THE WHITE LOCUS OF DROSOPHILA-MELANOGASTER

The white locus of D. melanogaster is a genetically well-characterized locus, mutations in which alter the degree or pattern of pigmentation of the eyes. Using a previously cloned DNA segment containing a portion of the white locus of a mutant allele, the DNA of a 48-kilobase chromosomal region of the Canton S wild-type strain was cloned and characterized. The positions, relative to restriction endonuclease cleavage sites, of several previously characterized chromosomal rearrangement breakpoints that bracket the white locus were mapped. A segment of 14 kilobases was defined containing all of the white locus sequences necessary for the production of a wild-type eye color phenotype. By conventional criteria, no repetitive sequences are present within this 14-kilobase segment; an extremely weak DNA sequence homology between a portion of this segment and a chromosomal region in the vicinity of the zeste locus was identified.