Binding of Corto on the Scr 10-kb Xba I fragment. (A) The 10-kb XbaI Scr fragment is located about 37-kb upstream from the transcription start site. Numbers refer to NT_033777, i.e. the access number of the complete sequence of the Drosophila melanogaster 3R chromosome. The 7 internal sequences (S1 to S7) and the two distal sequences (SL and SR) were amplified with specific primers as described in Methods. The PvuII and XmnI fragments, where DSP1 has been previously shown to bind, are in purple . (B) To determine the linear range of amplification, PCR samples were taken at the 29th, 31st, 33rd and 35th PCR cycles. (C-D) Chromatin immunoprecipitation analysis of 0–14 hour-old embryos (C) or S2 cells (D) using rabbit anti-Corto, rabbit anti-DSP1 or rabbit serum as a control (mock). The 31st cycle samples were loaded on a 1% agarose gel. The PCR products were quantified using Image J software and expressed as a percentage of the total input DNA. The diagrams represent the mean of 3 independent experiments.