Fig. 7. Structure of swellings under an electron (A,B) and a fluorescent (C,D) microscope. Part of the swelling in 56F (rectangular in A) is shown at higher magnification in B. An external envelope of the bubble is indicated by arrows with crosses; inner envelopes around small bubbles are indicated by straight arrows; and open thick arrow indicate the matrix within the bubble. A fluorescent Hoechst-33258-stained regular chromosome puff 71CF of the Oregon R strain (C) and swellings in regions designated by arrows in chromosomes of SuUR/SuUR Sgs3-GAL4 UAS-SuUR⁺ prepupae (D) are shown. Scales represent 1 µm (A) and 0.1 µm (B).