Fig. 2. In any one cell in a Drosophila salivary gland, trxG and PcG proteins alternatively associate with the bxd ME. (A) Variegating phenotypes of the white reporter gene of the 18-15 transgenic line in the salivary gland. DAPI staining of the same glands is shown in the lower panels. (B) Binding of trxG proteins Trx, Asx, Ash1 and Kis to chromosome 3 of the salivary gland polytene chromosomes of the wild type and 18-15 transgenic line. The site of insertion of the N construct is at the very tip of chromosome 3 and is indicated by arrowheads. Trx, Asx and Ash1, but not Kis, bind simultaneously to the site of insertion of the N construct in 50% of nuclei from the salivary glands prepared from the same larvae. (C) PcG proteins Ph, Pc and E(z) bind to the site of insertion of the N construct in those nuclei where Trx protein is not associated with this site.