bk1 << l(2)PC4-D << mama << bk2 << l(2)PC4-R

Fails to complement Df(2R)PC4, Df(2R)Pcl7B and Df(2R)Pcl11B, complements Df(2R)PC29, Df(2R)P34 and Df(2R)PC66.

Completion of mitosis 15 is abnormal, anaphase and telophase figures are not found. CycA and CycB staining reveals chromosome separation (chromosome disjunction) is defective. Entry into the next S phase occurs normally but staining reveals abnormal anaphase and telophase figures. Increase in cell size results from the polyploidisation during the progression through multiple cell cycles lacking chromosome separation and cytokinesis. Despite these abnormalities, major developmental events, such as germband retraction, proceed normally. Cell death occurs at very late stage with a higher frequency in mutants than wild type. The mitotic spindle is not defective in promoting the congression of the mitotic chromosomes into the metaphase plate. Later in mitosis only rudimentary signs of spindle elongation are detected. These irregular extended spindles are not accompanied by separation of the chromosomes. The centriole cycle is not affected.