Figure 4.—

Chromocenter size reflects satellite content. Stage 13 follicle cell nuclei were stained with DAPI (A, D, and G) and with antidimethyl histone H3 (B, E, and H). Chromocenters (arrows) stain as a bright DAPI dot within the nucleus and are enriched for lysine-9 dimethyl H3. The merged images (C, F, and I) show colocalization of DAPI and lysine-9 dimethyl H3. Bars, 10 μm. The area from each chromocenter was measured and normalized for nuclear area (J). Both DAPI (solid bars) and lysine-9 dimethyl H3 (shaded bars) area measurements show that, compared to D. melanogaster, D. virilis chromocenters are significantly larger (P < 0.0001) whereas C. pararufithorax has significantly smaller chromocenters (P < 0.0001). Standard error bars are shown and values represent averages from 35 cells (see materials and methods).