Mitotic index is decreased to 0.20% in homozygous larval brains, compared to 0.94% in wild-type brains. Two types of mitotic defects are observed; more common is mitotic figures with prematurely condensed chromosomes, while less common is figures showing precocious sister chromatid separation.

Polytene chromosomes in salivary glands in homozygous third instar larvae are underreplicated and banding is disrupted.

Homozygous larval brains show very little incorporation of BrdU.

The brains of mutant larvae do not halt progression through the cell cycle in response to either aphidicolin or hydroxyurea, in contrast to wild type, as they do not show a reduction in mitotic index.

The brains of mutant larvae do not show a drop in mitotic index after treatment with either etoposide or UV irradiation, indicating a failure to arrest the cell cycle.

Treatment with caffeine dramatically increases the mitotic index in mutant larval brain neuroblasts.

Mutant larval brain neuroblasts arrest in mitosis in response to treatment with colchicine, as occurs in wild type.

Homozygous larvae have no imaginal discs, suggesting a defect in imaginal disc proliferation.