Heterozygotes exhibit curly upturned wings, crossed posterior scutellars and darker than normal body colour. Transheterozygotes with U2 exhibit the same phenotype.
Viable over U2 and Df(2L)C'. Wing phenotype is additive with that of Cy1. Though originally described as causing upwardly curled wings, crossed posterior scutellar bristles, darker than normal body color with dark waxy wings, and eyes mottled with light flecks, only upturned wings, crossed posterior scutellars, and darker than normal body color are currently observed in U1 and U2 heterozygotes and U1/U2 heteroalleles. Since U1 is associated with a pericentric inversion with one break in proximal 2L heterochromatin, perhaps U1 was originally recovered in combination with a lt-bearing homologue and the eye mottling resulted from variegation associated with removal of the lt locus from its normal heterochromatic to a distal euchromatic environment in In(2LR)U; U1/lt- flies exhibit variegated eyes in addition to upturned wings, crossed postscutellar bristles, and darker body color.
Ball, 27th Jan. 1932.
Phenotype is incompletely penetrant, being less reliable in males than in females. Chromosome is homozygous lethal, due to a second site lethal mutation. Dp(2;Y)G does not cover the lethality of In(2LR)U.
Chromosome carries a second site lethal mutation located at neither the 40F or 53A breakpoints of the inversion. Phenotype exhibits reduced penetrance, depending on genetic background, being less reliable in males than in females.