Fig. 5. Analysis of PcG protein binding sites on the X chromosome. PcG-binding sites on polytene chromosomes were detected by immunofluorescent staining using primary antibodies directed against specific members of the PcG of genes. Secondary antibodies were Cy3-conjugated at 1:100 dilution (red). The DNA was labelled with DAPI (blue). An asterisks represents binding positions on the end of the X chromosome that do not change in the single or double mutants (with the exception of Pho, since all Pho bands are lost in the phol, pho double mutant). The arrow indicates the position of the 2D subdivision. (A) The binding pattern on chromosomes from wild-type (WT), or phol, pho double mutant larvae are shown for Pho, Pc, Psc, Scm and Ph. The Pc, Psc and Scm bands at the 2D position are lost in the phol, pho double mutants. (B) In E(z), a signal at 2D was seen only in about 20% of the wild-type chromosomes, and is not seen here. (C) Binding of Pc to the end of the X chromosome in pho and phol single mutants. The Pc 2D signal is not lost in pho or phol single mutants.

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