UAS regulatory sequences drive expression of the Scr C terminus containing the YPWM motif and the homeodomain (HD). The homeodomain carries amino acid substitutions T6D and S7D (these mutations have been shown to result in an inactive variant in the full-length protein) and Q50A and N51A (these residues normally participate in third helix binding of the HD to DNA).
Flies expressing ScrDD.Q50AN51A.Scer\UAS constitutively in the embryo, or ectopically in the antennal disc, do not display any abnormalities.