Brain neuroblasts in homozygous third instar larvae show high levels of aneuploidy. 55.7% of mitotic cells have overcondensed chromosomes. Few metaphase cells contain a well-formed metaphase plate and the majority of anaphase cells show lagging chromosomes and an unequal allocation of chromosomes. The ratio of mitotic cells in prometaphase/metaphase to those in anaphase/telophase is increased compared to wild type.

70.2% of mitotic cells in Spc25^mitch-1/Df(3R)ry75 larval brains have overcondensed chromosomes, and the mitotic index is reduced compared to wild type.

21.5% of mitotic cells in Spc25^mitch-1/Spc25^A34-1 larval brains have overcondensed chromosomes, and the mitotic index is reduced compared to wild type. The ratio of mitotic cells in prometaphase/metaphase to those in anaphase/telophase is increased compared to wild type.

Instead of arresting in mitosis, homozygous, Spc25^mitch-1/Df(3R)ry75 and Spc25^mitch-1/Spc25^A34-1 larval neuroblasts treated with colchicine prematurely enter anaphase and show a high incidence of precocious sister chromatid separation.

Homozygous larval neuroblasts treated with taxol show a high incidence of precocious sister chromatid separation, and have a significantly lower mitotic index than drug treated wild-type neuroblasts.

Homozygous and Spc25^mitch-1/Spc25^A34-1 spermatocytes show defects during the two meiotic divisions. Bivalent congression during meiosis I and II is disrupted and chromosome segregation during anaphase and telophase of both meiotic divisions is defective.