Deletion analysis of the vg Polycomb response element (PRE). (A) Eye phenotype of transgenic fly lines; 5-day-old male flies are shown. In each row, (top) heterozygous and (bottom) homozygous transgenic flies are shown, carrying the mw reporter alone (no PRE), the 1.6 kb vg PRE, a deletion of the first 106 bp (vg Δ100) and the first 291 bp (vg Δ300) of the 1.6 kb vg PRE, at landing sites (top) 2 and (bottom) 3. (B,D) Quantification of pigment levels of the heterozygous and homozygous transgenic vg Δ100 and vg Δ300 deletion lines at landing sites (B) 2 and (D) 3. (C,E) Pairing-sensitive silencing (PSS) of transgenic vg Δ100 and vg Δ300 deletion lines at landing sites (C) 2 and (E) 4, calculated as in Figure 3.