FIGURE 18-43 Chromosome movement and spindle pole separation in anaphase. Anaphase A movement is powered by microtubule-shortening kinesin-13 proteins at the kinetochore (A1) and at the spindle pole (A2). Note that the chromosome arms still point away from the spindle poles due to associated chromokinesin/kinesin-4 members, so the depolymerization force has to be able to overcome the force pulling the arms toward the center of the spindle. Anaphase B also has two components: sliding of antiparallel polar microtubules powered by a kinesin-5 (+) end–directed motor (B1), and pulling on astral microtubules by dynein-dynactin located at the cell cortex (B2). Arrows indicate the direction of movement generated by the respective forces. See Cleveland et al., 2003, Cell 112:407–421.