Imprecise excision of the progenitor insertion has resulted in a deletion that removes most of the Spc25 coding sequence, but does not extend into any other neighbouring genes.
Brain neuroblasts in Spc25A34-1/Spc2519B third instar larvae show high levels of aneuploidy. Many anaphase cells have lagging chromosomes.
82.3% of mitotic cells in homozygous 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 larval neuroblasts treated with colchicine prematurely enter anaphase and show a high incidence of precocious sister chromatid separation.
