Chromosome congression into a metaphase plate is slightly delayed in mitosis 16 in mutant embryos. The period from the onset of chromosome condensation until the metaphase-to-anaphase transition lasts longer than in controls (this delay occurs during prometaphase). Centromere positioning is more irregular in the mutants than in control embryos just before the onset of anaphase. After the metaphase-to-anaphase transition, some cells fail to achieve timely separation and/or segregation of one or two chromosomes (these nonsegregating chromosomes are not attached to the spindle in the normal bipolar fashion).