CLONING OF DNA-SEQUENCES FROM THE WHITE LOCUS OF DROSOPHILA-MELANOGASTER BY A NOVEL AND GENERAL-METHOD

The isolation of a cloned DNA segment carrying unique sequences from the white locus of D. melanogaster is described. Sequences within the cloned segment hybridized in situ to the white locus region on the polytene chromosomes of both wild-type strains and strains carrying chromosomal rearrangements in which breakpoints bracket the white locus. Two small deficiency mutations, deleting white locus genetic elements but not those of complementation groups contiguous to white, delete the genomic sequences corresponding to a portion of the cloned segment. The strategy employed to isolate this cloned segment exploits the existence of an allele at the white locus containing a copy of a previously cloned transposable, reiterated DNA sequence element. A simple, rapid method is described for retrieving cloned segments carrying a copy of the transposable element together with contiguous sequences corresponding to this allele. The strategy described is potentially general and its application to the cloning of the DNA sequences of other genes in Drosophila is discussed, including those identified only by genetic analysis and for which no RNA product is known.