Fig. 1. Identification of a novel gene with a segment polarity phenotype. (A-C) Cuticle preparations were visualized under dark field optics; anterior is towards the left, dorsal is upwards. (A) Wild-type embryos display a ventral cuticle with a segmentally repeated pattern of denticle belts and naked cuticle. (B) Segment polarity phenotype of a rasp GLC-derived embryo lacking both maternal and zygotic contributions. Note the reduction in naked cuticle and the lawn of denticles. To identify unambiguously the genotype of the embryos that have received a paternal wild-type copy of rasp, we recombined the rasp chromosome with a mutation in trachealess (trh). trh results in embryos with a mutant Filtzkorper as described previously (Haecker et al., 1997). Note the Filtzkorper in rasp, trh/rasp, trh mutant embryos. (C) Cuticle preparation of rasp, trh/+ GLC-derived embryos that carry a wild-type paternal chromosome. The paternal rescue was often complete and cuticles were indistinguishable from those of wild-type embryos (compare A with C).