The prometaphase

      The definitive mitotic spindle is formed and the chromosomes are moved into position at the center of the cell  :       It is suggested that the longer microtubules exert greater tension than the shorter microtubules, and as a result, the chromosome tends to be pulled toward the pole from which the longer microtubule has extended. As the chromosomes move toward the center of the mitotic spindle midway between the poles, the longer microtubules are shortened as a result of disassembly while the shorter microtubules are elongated by the addition of tubulin subunits. Eventually, each chromosome is moved into the position along a plane at the center of the spindle, so that the microtubules from each pole are equivalent in length.