Position effect variegation caused by transposition of A(R)4-24P[white, rosy] in the Drosophila melanogaster genome

A line with the mosaic expression of the white(+) transgene was obtained by inducing transposition of the A(R)4-24P[white, rosy] transposon and was us ed for the second round of induction. As a result, 57 lines with the mosaic eye pigmentation were obtained. In situ hybridization and Southern blottin g showed that genomic DNA fragments flanking A(R)4-24 were, in some cases, transposed together with the transposon. A spontaneous loss of these fragme nts resulted in reversion to the wild-type phenotype. The mosaic eye pigmen tation in a line that carried the A(R)4-24 transposon flanked with the same fragments in region 24D1-2 was not affected by the Su(var)3-6 gene modifyi ng position effect variegation (PEV). Other PEV modifiers, Su(var)3-9 and S u(var)2-5, had only a slight effect on PEV; Su(var)3-7 restored the wild-ty pe phenotype. The genomic fragments captured by the transposon may contain DNA sequences that autonomously induce mosaic PEV of the white gene.