drosha^21K11/Df(2R)Exel6055 transheterozygous animals all die at the larval-to-pupal transition. Approximately 10% die as late-stage larvae, whereas the remainder unsuccessfully attempt to pupariate. These animals exhibit a small central nervous system and lack imaginal discs.

drosha^21K11 mutant MARCM mushroom body clones contain significantly fewer neurons in adult flies compared to controls, with those neurons present being predominantly early born γ neurons. These mushroom bodies also contain a handful of α'/β neurons but no α/β neurons. Axonal extensions of the rare α'/β neurons are frequently mistargeted, innervating inappropriately near α/β lobe termini.

Homozygous anterodorsal projection neuron (adPN) clones show a modest reduction in cell number compared to controls when analysed at the adult stage.

7 days old females carrying homozygous germline clones result in egg chambers with 8 nurse cells and no oocyte with 48% penetrance.

Homozygotes die as third instar larvae or poorly formed early pupae. Mutant third instar larvae almost completely lack imaginal disc structures.