Fig. 2. Anaphase B kinetics are similar between klp67A mutants and wild-type cells. Selected frames from time-lapse series comparing anaphase B in a wild-type (A) and klp67A mutant primary spermatocyte (B) expressing ß-tubulin-EGFP. The maximum intensity projection of the six optical sections and the corresponding single, centre-most DIC image for each time point is shown here and a similar format is used for subsequent figures. (A) In wild-type cells anaphase B occurs after the dyads disjoin (0 minutes). Once initiated, the spindle continually elongates, moving the centrosomes in opposite directions until a new steady-state length is reached (10-18 minutes) (B). (B) Before anaphase onset (0 minutes) klp67A mutants formed dense spindles surrounded by long astral microtubules. Unlike in control cells, the centrosomes in the mutants did not undergo significant separation during anaphase B. As the spindle elongated (5-13 minutes) it buckled out of this focal plane before also assuming a new steady-state length (18 minutes). Note how the mutant lacks a discreet central spindle. See main text for details. (C) Kinetic plot of the elongating spindles depicted in (A) and (B). In both cases there is a lag before anaphase B initiates, after which time the spindles extend at the indicated velocities. See Materials and Methods for details of measurements. Bar, 10 µm. Times are in minutes relative to anaphase onset.