Fig. 1.

Schematic representation of the y2 allele. Exons of the yellow gene are shown with rectangles, with an arrow indicating the direction of transcription; EnW – wing enhancer; EnB – body enhancer; EnBr – bristle enhancer; and Pr – promoter of the gene. The gypsy retrotransposon is depicted as a triangle; the rectangles at its ends are long terminal repeats, with their direction shown with arrows. The Su(Hw) insulator is depicted as a hexagon inside gypsy. The photographs show the phenotypes of flies: y+ – wild type, the yellow gene is expressed in all cuticular structures; y2 – body and wing enhancers are blocked by the Su(Hw) insulator (depicted as strikethrough); the yellow gene is not expressed in the body cuticle and wings but continues to be expressed in the bristles