The FRT cassette has been excised, allowing expression of the dpp coding region under the control of the dpp disc (D) enhancer, in which all three ci protein binding sites (low affinity) have been altered to match the sequence of the high-affinity ci protein binding site found in the ptc enhancer.
Expression of dppD-ci.ptc causes lethal developmental defects, including severe head and limb deformities and pupal lethality resulting from overgrowth fusion, and patterning defects in antenna and leg discs.