Fig. 1. ft and ds regulate planar polarity. (A) Wild-type dorsal (D) and ventral (V) ommatidia. At the five-cell stage, preclusters rotate in opposite directions to assume D and V polarity. Outer photoreceptors are recruited into the clusters as pairs and share similar characteristics, indicated by similar colors in the R1/6, R2/5 and R3/4 cells. Dorsal is upwards and anterior is leftwards. (B) Smooth edges of mitotic clones of ft^Albert (arrows). All ft alleles examined had smooth edges, planar polarity defects and enhanced growth in clones. (C-E') Sections (C-E) and schematic diagrams (C'-E') of wild-type, and ft and ds mutant fly eyes. In the wild-type eye (C,C') the trapezoid shapes formed by the photoreceptor rhabdomeres of the D ommatidia point upwards (red arrows), the V ommatidia (blue arrows) point in the opposite direction; D and V fields are separated by a division known as the equator (yellow line). In ft^fd/ft^chance transheterozygous (D,D') and ds^UAO71 homozygous mutants (E,E'), D and V ommatidia are intermixed and no obvious equatorial line can be drawn. (F,G) Sections of ft^fd and ds^UAO71 mutant clones and (F',G') diagrams of PP. ft^- and ds^- tissue are marked by the absence of pigment. White arrows indicates wild-type ommatidia on the polar (F) or equatorial (G) sides of the clones, non-autonomously affected by the clones. Red and blue arrows (F',G') indicate ommatidia with D and V polarity, respectively, in these and in all remaining panels.