Translocation breakpoint disrupts the transcription unit between exons 1 and 2.
Reduced brain volume, neuronal architecture has no gross alterations. External appearance is wild type, body size is slightly smaller than wild type. Mutants require 10% more time for their development and have considerable difficulty escaping from the pupal case. Adults exhibit defects in olfactory and visual behaviour. The neuroblast proliferation centre in larval brains is altered, unable to generate sufficient numbers of optic lobe and central brain neurons.