Fig. 3. Phenotype and Abd-B and lacZ expression of class I derivatives. (A) Posterior abdominal segments of an Abd-B^T2N/DfP9 male (Abd-B^T2N is a class I derivative), showing the transformation of the A7 and A8 segments. Note the large size of the A7 (absent in wild-type males) and the small A8. G, male genitalia. (B) Abd-B protein expression (violet/black) and ß-galactosidase expression (orange) in a stage 10 Abd-B^T2N homozygous embryo. While Abd-B expression is confined to PS14 (Abd-B R protein), ß-galactosidase signal is strong in PS13. Numbers indicate PS.