Anaphase

Anaphase, from the ancient Greek ἀνά (up) and φάσις (stage), is the stage of mitosis or meiosis when chromosomes move to opposite poles of the cell.

Anaphase accounts for approximately 1% of the cell cycle's duration. It begins with the regulated triggering of the metaphase-to-anaphase transition. Metaphase ends with the destruction of cyclin, which is required for the function of metaphase cyclin-dependent kinases (M-Cdks). Anaphase is initiated with the cleavage of securin, a protein that inhibits the protease known as separase. Separase then cleaves cohesin, a protein responsible for holding sister chromatids together.

During early anaphase (or Anaphase A), the chromatids abruptly separate and move toward the spindle poles. This movement is caused by the shortening of spindle microtubules. The force is being exerted at the kinetochore.

When the chromatids are fully separated, late anaphase (or Anaphase B) begins. This involves the polar microtubules elongating and sliding relative to each other to drive the spindle poles to opposite ends of the cell. Anaphase B drives the separation of centrosomes to opposite poles through three forces. Kinesin proteins that are attached to polar microtubules push the microtubules past one another. A second force involves the pulling of the microtubules by cortex-associated cytosolic dynein. The third force for chromosome separation involves the lengthening of the polar microtubules at their plus ends.

These two processes were originally distinguished by their different sensitivities to drugs, and they are mechanically distinct.
 * Anaphase A involves the shortening of kinetochore microtubules by depolymerization at their plus ends. During this process, a sliding collar allows chromatid movement. No motor protein is involved, as ATP depletion does not inhibit early anaphase.
 * Anaphase B involves both the elongation of overlapping microtubules and the use of two distinct sets of motor proteins: one pulls overlapping microtubules past each other, and the other pulls astral microtubules that have attached to the cell cortex.