Lethal in combination with Df(3R)L16, with larvae dying at the third instar stage. Although T(Y;3)B197/Df(3R)L16 is lethal, this combination no longer shows the cell cycle arrest phenotype described in FBrf0049898, presumably due to the accumulation of modifiers. It is therefore not possible to ascertain whether the cell cycle aspect of the phenotype of T(Y;3)B197/Df(3R)L16 animals is due to lack of Osbp.

Third instar larval brains have a phenotype typical of mitotic mutants leading to metaphase arrest during prometaphase or metaphase. The similarity of phenotypes between asp and mar suggests mar may be involved in spindle function. mar¹ does not interact with βTub85D. Slight maternal effect on viability suggests possible involvement of maternal effect of mar with zygotic component of asp.

All cells arrested at metaphase are diploid.

cells in larval brain have highly condensed X-shaped chromosomes, a mitotic index twice that of wild type and a thirty-fold reduction in the ratio of anaphases to metaphases. Only about 1% of cells are tetraploid, the remainder remaining diploid. Complements asp, which is just to the left. L3 larval lethal (hemizygotes)