Fig. 1. fmi and pk mutations dominantly modify the sev-stbm eye phenotype. Tangential sections through adult eyes are shown in the top part of each panel and a schematic is given below, in which different chiral forms are shown in different colors. (A) In wild-type adult eyes, ommatidia in the dorsal hemisphere are oriented towards the dorsal pole while those in the ventral hemisphere are oriented towards the ventral pole. These fields of opposing ommatidial chirality are separated by the equator (yellow line). The inset illustrates the position of photoreceptors R1-R8 in a single ommatidium. (B-E) All sections are from the dorsal half of the eye. (B) sev-stbm. About 10% of ommatidia display errors in polarity, as illustrated by differently colored trapezoids. (C,D,E) Mutations in fmi enhance the sev-stbm phenotype. (C) sev-stbm/+; fmi^frz3/+, (D) sev-stbm/+; fmi¹⁹² /+, (E) sev-stbm /+; fmi^E59/+. Three fmi alleles, fmi^frz3 (a hypomorphic allele), fmi¹⁹² and fmi^E59 (both null alleles) dominantly enhance the sev-stbm phenotype about 3 fold. Yellow forms in the schematics denote symmetrical defects. (F) A hypomorphic pk allele, pk^pk1, enhances the sev-stbm phenotype about 2.5 fold. (See Table 1 for quantitative data.) Blue and red trapezoids represent ommatidia in the dorsal and ventral hemispheres, respectively. Anterior to the right.