Homozygotes die as late third instar larvae or pupae. Larval brains are normal in size. The mitotic index of mutant larval neuroblasts is increased compared to wild type. The proportion of cells in early mitotic stages (prophase and prometaphase) is increased and the proportion of cells in late mitotic stages (metaphase, anaphase and telophase) is decreased in the mutant cells compared to wild type. Chromosomes are undercondensed in the mutant neuroblast cells.

gwl⁷¹⁶/gwl¹⁸⁰ larval brains are normal in size. The mitotic index of mutant larval neuroblasts is increased compared to wild type. The proportion of cells in early mitotic stages (prophase and prometaphase) is increased and the proportion of cells in late mitotic stages (metaphase, anaphase and telophase) is decreased in the mutant cells compared to wild type.

Some adult gwl⁷¹⁶/gwl¹⁸⁰, gwl⁷¹⁶/gwl¹⁰⁸⁰ and gwl⁷¹⁶/gwl²⁷⁹⁰ escapers are seen. These eclose several days late and have rough eyes and wing defects. The females are sterile and do not lay eggs. The males are sterile.

Prophase in gwl⁷¹⁶ mutant neuroblasts lasts >10 times longer than in controls. After nuclear envelope breakdown, mutant cells are ~2 times slower than controls to reach metaphase, with ~20% of mutant cells nevering achieving stable metaphase. The duration of metaphase is also over 4 times longer in gwl⁷¹⁶ neuroblasts than in controls. Chromosome condensation takes much longer in colchicine-treated gwl⁷¹⁶ cells than in similarly treated controls, with ~30% of gwl⁷¹⁶ cells failing to condense their chromosomes fully or initiate nuclear envelope breakdown during periods exceeding 4 hours.