Fig. 2. Misexpression of homeotic genes and homeotic transformations in Su(z)12 mutant embryos. (A,B) Embryos at stage 16 (A) and stage 11 (B) stained with antibody against Ubx protein. In wild-type (wt) embryos, Ubx is expressed from parasegments (ps) 5 to ps 13 (anterior margin of ps 5 in all cases marked by an arrowhead) and in five midline cells in ps 4 (visible in A). (A) Su(z)124 homozygous embryos (zyg-) show misexpression of Ubx anterior to ps 5 but only in a few cells in the CNS and in the brain (asterisk); more extensive misexpression of Ubx is seen in ps 1-4 of Su(z)121 homozygotes. (B) Su(z)122/Df(3L)kto2 embryos derived from Su(z)122 germline clones show strong expression of Ubx from ps 1 to ps 14 already at this earlier stage owing to the lack of both maternal and zygotic (mat- zyg-) wild-type Su(z)12 protein. (C) Cuticles of a wild-type and a Su(z)12 mutant embryo of the same genotype as in B. In the Su(z)12 mutant embryo all abdominal, thoracic and several head segments (not all visible in this focal plane) are homeotically transformed into copies of the eighth abdominal segment owing to misexpression of the Abd-B gene in every segment (the eighth abdominal segment is marked by an arrow in the wild-type embryo and the first abdominal segment is marked by a white arrowhead). Su(z)125/Df(3L)kto2 embryos derived from Su(z)125germline clones show similar misexpression of Ubx and cuticle phenotypes like the embryos shown in B and C (data not shown).