Figure 1 .

Design and results of the screen. (A) During larval development of flies heterozygous for an EMS-induced mutation (*), ey-FLP induces mitotic recombination between FRT sites on duplicated homologous chromosomes. Chromatid segregation at mitosis can produce daughter cells homozygous for the mutation (*/*). In the adult eye, a P(w+) element on the wild-type chromosome allows homozygous mutant clones to be recognized by their lack of red pigment. (B) EMS-mutagenized FRT19A males were crossed to P[w+, ubi-GFP], ey-FLP, FRT19A females. Induction of the cell death gene head involution defective (hid) present on the Y chromosome by heat shock (HS) ensured that the F1 daughters screened were virgins. Selected females were mated to FM6, w, and then FM7i, pAct-GFP marked balancers to establish F3 mutant stocks. Four independent stocks for each mutation were retested by crossing to the ey-FLP line (F4). (C–H) Adult eyes showing mutant phenotypes. Ommatidia fail to differentiate in 3B1 clones (C), and transform into scars in 4A1 clones (D) or cuticle outgrowths in sgg^3B5 clones (E). Males hemizygous for fw^1B2 display reduced, bumpy eyes (F), while the retina of lz^4B4 males is smooth and glossy (G). Ectopic antennae form in 8D2 mutant clones (H).