FIG. 1.

Schemes of the transgenic constructs and analysis of transgenic lines for the ability of Su(Hw) insulators to interact across interposed elements. The Su(Hw) insulators are shown as black circles marked I. The yellow enhancers (Ey) and the additional promoter (Py) are shown as white boxes. The 1.5-kb DNA spacer fragment (S) is shown as a thick black line. The yellow and white genes are framed, with arrows indicating the direction of transcription. The frt and lox sites are shown as black and white triangles, respectively, in the schemes and are denoted by parentheses in construct names. The data below the schemes give the numbers of transgenic lines with the specified (top) y pigmentation levels in the abdominal cuticle (reflecting the activity of the body enhancer); in most of the lines, the pigmentation levels in wing blades (reflecting the activity of the wing enhancer) closely correlated with these scores. N is the number of lines in which flies acquired a new y phenotype upon deletion (Δ) of the specified DNA fragment; T is the total number of lines examined for each particular construct.