The nuclei of mutant early embryos are abnormally shaped and increased in size compared to controls. The nuclei fail to become properly aligned in a single layer below the cortical membrane of the preblastoderm embryo. Deep folds are seen in mutant blastoderm embryos, which remain in pregastrulating embryos. The region adjacent to the folds is marked by enlarged nuclei in the embryos. Giant cells containing multiple dividing nuclei are occasionally seen, indicating incomplete cytokinesis.
The synchronous mitotic wave normally seen in blastoderm embryos is abnormal in hemizygous embryos. Defects range from abnormal starting points of the waves and include asynchronous divisions as shown by a "salt and pepper" distribution of nuclei that are in different mitotic stages. DNA replication is also asynchronous.
