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DVDY_21981_sm_SupFigS1.tif1711KSupp. Fig. 1. Extant hbs alleles have second site modifiers. Tangential sections of adult eyes and corresponding schematics. A: Wild-type eye. Blue circles are the rhabdomeres, or photosensitive membranes of the photoreceptor cells; blue trapezoids in schematics connect the rhabdomeres to emphasize ommatidial orientation. Blue trapezoids identify ommatidia with wild-type chirality. B–D: Photoreceptor number defects (black asterisks) in multiple hbs alleles appear to be due to a background mutation. B: hbs459/hbs2593 ommatidia exhibit the expected orientation defects (0.8%) in addition to unexpected missing or extra photoreceptors (16.8%). Similar phenotypes are seen in (C) hbs459/Δ12 (2.0% tissue polarity defects and 16.6% missing/extra R cells) and (D) hbs2593/Δ12 (2.0% tissue polarity defects and 16.6% missing/extra R cells). A rare inversion on both anterior/posterior and dorsal/ventral axes is designated by a black trapezoid in C. E: Ommatidia in an outcrossed line derived from hbs459 (hbs459*) have a full complement of photoreceptors (3.3% missing/extra R cells). Ommatidia are frequently oriented somewhat off-axis, and rare tissue polarity-type defects are evident (0.8%; yellow forms represent R4/R4-type symmetrical ommatidia), phenotypes that are seen in the hbs alleles described here.

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