hobo-induced rearrangements are responsible for mutation bursts at the yellow locus in a natural population of Drosophila melanogaster

In 1981 recurrent local bursts of mutability of the yellow gene were observ ed in a natural population of Drosophila melanogaster from Uman' (Ukraine). A series of y(2)-like mutations in the yellow gene were recovered during t he period 1982 to 1991. Most of the mutants display the y(2)-phenotype, i.e . mutant yellow color of wings and body cuticle. Ninety-nine y(2) mutants w ere shown to be generated by an inversion that occurred between two hobo el ements, one located 129 bp from the start site of yellow transcription, and the other in the distal telomere region. The y(2) phenotype was caused by the separation of the body and wing enhancers from the transcription unit. Many of the y(2)-like alleles were highly unstable and reverted to y(+), wh ich again, gave rise to y(2)-like mutants. We found that the y(2) --> y(+) --> y(2) transitions were generated by repeated inversions between the two hobo elements mentioned. The y(2) Land y(+) alleles lost their instability after deletion of the hobo element present at the tip of the X chromosome.