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Figure 3


Fig. 3. PRE action over a distance. (A) Location of P[en2] in line P[en2]-E(Pc). Thick line indicates genomic DNA. Arrows below the line indicate the extent and direction of transcription of E(Pc), inv and en. Black box above the line indicates the location of the PSE1 and PSE2 DNA in the genomic en gene. Arrow above the line denotes the location of P[en2] in the E(Pc) gene. (B) Immunoperoxidase staining showing β-gal protein in the starting line P[en2]-E(Pc) and in P[en2]-E(Pc){Delta}both. β-Gal is expressed in only a few cells between the stripes in P[en2]-E(Pc){Delta}both, in contrast to the massive misexpression seen at other chromosomal locations (see Fig. 2I). Embryos are anterior leftwards, dorsal upwards, 10 hours AEL. (C) X-gal staining of wing discs from P[en2]-E(Pc) and its Flp and/or Cre recombinase-treated derivatives. β-Gal activity in the posterior compartment (where en is normally expressed) is largely dependent on the presence of PSE1 or PSE2, although a small amount of β-gal activity remains in the {Delta}both derivative.