Hemizygous mutant embryos show a "buttonhead"-type appearance. The terminal larval cuticle shows defects in head involution and ventral denticle patterning. The fifth-through-seventh abdominal denticle belts are missing or fused.

Ectopic thoracic-like hairs are present anterior to the normal rows of first thoracic dorsal hairs in hemizygous mutant embryos.

Hemizygous mutant embryos show fusion of the labial and thoracic segments with labial tissues developing as first thoracic, yielding an enlarged first thoracic segment. The first thoracic denticle belt appears to form at the labial/maxillary border. The anterior denticle row of the first thoracic segment is directly adjacent to the maxillary cirris in some cases. The denticle belt is frequently split at the ventral midline.

Approximately 20% of hemizygous mutant embryos show homeosis of the labial segment to yield two nearly complete first thoracic segments. Labial and thoracic segments do not fuse in these cases, and complete duplication of the first thoracic denticle belt is present in the transformed labial segment.

The dorsal ridge usually remains visible in hemizygous mutant embryos, but is fused in part to the dorsal labial segment.

Muscle pattern wild type within constraints imposed by alterations in body plan. Muscles contractile and vigorous.

gt^Q292/gt^E6 larvae synthesise DNA of a reduced molecular weight, have an unusually high frequency of spontaneous single and double-strand breaks, and shows a reduction in the normal inhibition of DNA synthesis following treatment with UV. gt^Q292/gt¹ larvae show a reduction in the normal inhibition of DNA synthesis following treatment with N-acetoxy-2-acetylaminofluorene.