From zimm@XXXX Fri Jan 26 05:06:57 1996 Date: Thu, 25 Jan 1996 21:00:24 -0800 (PST) From: Georgianna Zimm <zimm@XXXX> To: flybase-updates@XXXX Content-Transfer-Encoding: 7BIT Content-Length: 4047 Zimm, G.G. and D.L Lindsley. Department of Biology, University of California, San Diego, La Jolla, CA 92093-0322. Upturned revisited with description of a new allele. Among the progeny of phenotypically wild-type males treated with ethyl methanesulfonate, one fly with curly wings was recovered; the phenotype was subsequently inherited as a dominant mutation that segregated with chromosome 2; crossing over with al b c px sp was normal, and no straight-winged recombinants with c (2-75.5) were recovered among 161 testcross progeny. This result places the new mutation in the vicinity of Upturned (U). The allele U is associated with a pericentric inversion with breakpoints at 40F and 53A according to Bridges and Li (Morgan, Bridges, and Schultz, 1935). The genetic map position originally given for U was 70+/- based on the mapping of a putative second allele, U[H20], isolated by Tanaka (1937); more recently Ashburner has revised this position to 2-, based on the 53A breakpoint of In(2LR)U, (FlyBase, 1994). In(2LR)U is homozygous lethal, and U[H20], now lost, was homozygous viable. The new mutation is also homozygous lethal, but it survives in heterozygous combination with U. If the new mutation is an allele of U, then at least one of the above two is not a lethal allele. To clarify this ambiguity, we generated an X-ray-induced revertant of U and found that it is lethal in combination with the new mutant; thus we conclude that the new mutation is a lethal allele of U, whereas U is a viable allele with a lethal mutation elsewhere on the chromosome; we designate the new allele U. U/U, U/Cy , and U/Cy flies show an additive effect of the curly-wing phenotype. We have been unsuccessful in finding a deficiency that uncovers the lethality of U. The fact that neither four deficiencies for c at 52D1-7 (Saxton, pers. comm.; FlyBase, 1994) extend far enough to the right to include 53A, coupled with our inability to establish stocks of nearly all Xray-induced revertants of either U or U, implies the existence of haplo-insufficiency that is coincident with or closely linked to Upturned. No duplications are available to cover the 53A1 breakpoint of In(2LR)U. The viability of U over Df(2L)C', a deficiency for the 2L heterochromatin (Hilliker and Holm, 1975), indicates that the lethal mutation in In(2LR)U is not associated with the breakpoint at 40F. We were unable to cover the lethality of U in male homozygotes with Dp(2;Y)G, a duplication that includes the 40F salivary region. In our hands U (but not U) exhibits reduced penetrance, with its expression depending on genetic background and in general being less reliable in males than in females. In the original description (Bridges, 1935), U was said to cause, in addition to upwardly curled wings, crossed posterior scutellar bristles, darker than normal body color with dark waxy wings, and eyes mottled with light flecks. Of these phenotypes only upturned wings, crossed posterior scutellars, and darker than normal body color are currently observed in U and U heterozygotes and U/U heteroalleles. Since U is associated with a pericentric inversion with one break in proximal 2L heterochromatin, we speculated that perhaps U was originally recovered in combination with a lt-bearing homologue and that the eye mottling was variegation associated with removal of the lt locus from its normal heterochromatic to a distal euchromatic environment in In(2LR)U; U/lt flies exhibit variegated eyes in addition to upturned wings, crossed postscutellar bristles, and darker body color. References: Bridges, 1935, DIS 3: 5-19; Bridges, 1937, DIS 7: 5-17; Davis and MacIntyre, 1988, Genetics 120: 755-66; FlyBase, 1994, Nucleic Acids Res. 22: 3456-58; Hilliker and Holm, 1975, Genetics 81: 905-21; Morgan et al., 1935-36 , Year Book - Carnegie Inst. Washington 35:289-97 ; Saxton, pers. comm.; Tanaka, 1937, DIS 8: 11.