Immunofluorescence analysis of polytene chromosomes in RNA Pol II 140 and small RNA pathway mutants. Representative images from five different experiments (approx 50 pairs of nuclei) have been examined. The genotypes of each polytene nuclei have been indicated. The FITC (green) channel shows H3K9me2 antibody signal while the Texas Red shows Sxl antibody signal. H3K9me2 staining at the chromocentre is displayed.