Lindsley & Grell, 1972, p. 100
discoverer: Bridges, 12k4.
references: Morgan and Bridges, 1916, Carnegie Inst. Wash. Publ. No. 237: 55-58 (fig.). Lynch, 1919, Genetics 4: 501-33.
phenotype: Veins L3 and L4 fused from base to beyond anterior crossvein, with elimination of anterior crossvein and first basal cell; L3 and L4 fused at tip; this fusion may reach back to basal cell. Wings usually extended. Ocelli reduced or absent; bristles of ocellar region small or absent. Eyes small and slightly rough. Anterior scutellar bristles reduced in number, and scutellum shortened. Female late to eclose and has decreased longevity. Ovaries histologically normal at eclosion but with half the normal number of ovarioles (Beatty, 1949, Proc. Roy. Soc. Edinburgh, B 63: 249-70); fecundity 7 percent normal. Developing egg chambers may fuse or become tumorous with age [King, Burnett, and Staley, 1957, Growth 21: 239-61 (fig.)]. Proportion of tumorous egg chambers increases by 6 percent per day. Female raised at l8oC shows only 10 percent the tumor development of that raised at 25o. Ovarian effects in female carrying fu and a deficiency for fu [i.e., In(1)ClLy4R = In(1)4A5-B1;17A6-B1L1A8-B1;18A3-4R] are more extreme than those in fu homozygote (King, 1959, DIS 33: 142-43). fu/fu ovaries transplanted into fu+ hosts develop autonomously in regard to fertility (Clancy and Beadle, 1937, Biol. Bull. 72: 47-56; Sobels, 1950, Experientia 6: 139-40) and tumor formation (Bodenstein and King, 1963, DIS 37: 65). The few normal-appearing eggs that are laid by fu/fu females produce adults only if they have been fertilized by fu+-bearing sperm (Lynch, 1919, Genetics 4: 501-33). Eggs fertilized by fu- or Y-bearing sperm develop into embryos that become abnormal 5-51/2 hr after fertilization. A general asymmetry in germ layers is responsible for many ensuing abnormalities. Such embryos never hatch but survive long after normal embryos have become larvae [Counce, 1956, Z. Induktive Abstammungs-Vererbungslehre 87: 462-81 (fig.)]. fu eggs from fu/+ mothers develop normally. Heterozygous daughters from homozygous mother have high incidence of abnormal abdominal segmentation and, as embryos, have abnormal musculature. This is a maternal effect not found in the reciprocal cross, and it is temperature sensitive (Armstrong and Sobels). RK1.
cytology: Salivary chromosome location of fu appears to be in 17D or E (Green, 1953, Genetics 38: 91-105; 1953, Z. Induktive Abstammungs-Vererbungslehre 85: 435-49).
color figure: P. A. Otto (original)
b & w figure: Morgan, Bridges and Sturtevant, 1925, The Genetics of Drosophila, Bibliog. Genet. 2: 1-262 (original drawn by Edith M. Wallace)