Precise inversion of the starting P{(-FRT)lacZ.HP}UbxHC184B element.
Homozygous flies show a fairly complete transformation of the dorsal first abdominal tergite towards the character of the second abdominal segment; the A1 tergite is enlarged and has bristles and pigmentation like that of the A2 segment. There is a sternite in the A1 segment (the first abdominal segment lacks a sternite in wild-type flies), although it is not completely transformed to a more posterior type. Heterozygotes also show transformation of the first abdominal segment into a copy of the second abdominal segment.
Distally directed transcripts from the P{(-FRT)lacZ.HP}abd-AUab-R1 insertion are detected in abd-AUab-R1 embryos.