Site specificity of mutations arising in dysgenic hybrids of Drosophila melanogaster.

Abstract

Mutations arising in dysgenic hybrids of D. melanogaster were collected in the zeste-white region of the X chromosome. A preponderance of the mutations affected the zw1 locus; many of these were associated with structural abnormalities including inversions, deficiencies and insertions in the 3A3-4 region of the polytene chromosome map. The extreme sensitivity of the zw1 locus to the mutator activity of dysgenic hybrids contrasted with the apparent insensitivity of the zw2 locus. Other loci in the zeste-white region were weakly sensitive to the mutator activity. Insertions of 2 and 6 bands were seen between bands 3A4 and 3A6 in the chromosomes of one of the zw1 mutant stocks examined. Another insertion was detected at position 2F4-5 in a different stock. Many of the mutant chromosomes were evidently unstable, as judged by secondary breakage in other parts of the X chromosome. Mutations arising in dysgenic hybrids may be caused by transposable elements which insert preferentially at certain sites on the chromosomes.