Fig. 3. omb interacts genetically with ab. (A) A homozygous ab¹/ab¹ mutant wing lacks the distal section of L5. (B) Heterozygous ab¹/+ flies have a fully penetrant wild-type wing phenotype. (C) Heterozygous omb¹/+ flies also have a fully penetrant wild-type wing phenotype. (D) An omb¹/omb¹ mutant female wing has a notched wing margin, but no L5 truncation. (E) A brk^m68/+; ab¹/ab¹ wing has a phenotype similar to that of ab¹/ab¹ homozygotes. (F) A trans-heterozygous omb¹/+; ab¹/+ female wing with a distal L5 truncation. This is a reproducible phenotype that occurs with low penetrance (3%). (G) An omb¹/+; ab¹/ab¹ female wing has an enhanced L5 vein truncation relative to that observed in ab¹/ab¹ controls (compare with A). (H) An omb¹/Y; ab¹/ab¹ double mutant male wing has a greatly enhanced L5 truncation phenotype relative to that observed in ab¹/ab¹ flies (compare with A).