Homozygous embryos show ectopic crossing of the midline by axons in the central nervous system.

Homozygotes show a delay in development of a number of days in crowded culture. Homozygous females lay fewer than 10% of the eggs of wild-type females, the numbers decreasing markedly as the females age. Homozygous ovaries show degeneration and contain fewer eggs than wild-type. Approximately one third of eggs derived from homozygous females have no nuclei, and of the remainder, more than 90% show perturbation of the uniform distribution of the nuclei. 10-20% of embryos derived from homozygous females cellularise, at least partially, but less than 1% hatch. Homozygous males are sterile. Syncytial embryos derived from homozygous females have regions devoid of nuclei in metaphase that contain free centrosomes that nucleate asters of microtubules (in contrast to the wild-type regular distribution of mitotic spindles). Additional centrosomes appear to become incorporated into spindles to form multipolar structures. Free centrosomes are also seen in fields of anaphase figures, in which the spindles are frequently excessively curved, bent and sometimes wavy. This defect appears accentuated at telophase, where midbodies are sometimes disoriented so that they are aligned at 90^o rather than 180^o to each other. Some nuclei appear to contain more than a diploid amount of DNA, and nuclei connected by thin chromatin bridges are also occasionally seen. Hemizygotes show reduced viability and show abnormal adult external morphologies typical of cell cycle mutants, including slightly roughened eyes, thin and short bristles and, less frequently, notched wings. Mitotic defects are seen in the cells of the larval central nervous system in homozygotes. Approximately 6% of total metaphase cells contain more than a diploid complement of chromosomes. The overall mitotic index is almost 3 times higher than wild type and the proportion of diploid cells in metaphase to anaphase is 2 times higher than in wild type, indicating a delay in the passage through this mitotic transition. The majority of the polyploid figures and 18% of the diploid figures contain hypercondensed chromosomes. The level of hyperploidy of most cells does not exceed 8N. Circular mitotic figures, with all the major chromosomes arranged in a circle with their centromeres inward and arms oriented towards the periphery and the fourth chromosome at the centre, are occasionally seen. These appear to correspond to monopolar spindles in which condensed chromosomes are arranged around a single centrosome in the same plane. Monopolar figures in which chromatids appear as if pulled towards a single pole are also seen. Polyploid sets of chromosomes are frequently associated with spindles that are multipolar.