P{lArB} element insertion in the 5' UTR.
Mutant egg chambers show defects in karyosome morphology; often the nuclear material is split into two or three lobes.
Eggs derived from hemizygous females show a cold-sensitive ventralised egg-shell phenotype. More than 95% of the ventralised eggs have a single dorsal appendage at 18oC.
Follicle cells do not differentiate properly, egg chambers have too many or too few nurse cells. Eggs that are laid have chorion defects.