Telophase

Date: 2015-10-07; view: 431.

Anaphase

When every kinetochore is attached to a cluster of microtubules and the chromosomes have lined up along the metaphase plate, the cell proceeds to anaphase (from the Greek ανα meaning "up," "against," "back," or "re-").

Two events then occur: first, the proteins that bind sister chromatids together are cleaved. These sister chromatids now become separate daughter chromosomes, and are pulled apart by shortening kinetochore microtubules and move toward the respective centrosomes to which they are attached. The cleaved centromeres go first while the chromatids trail behind. They all look like they're trying to grab at their partners, because they become shaped like a V.

Next, the polar microtubules elongate, pulling the centrosomes (and the set of chromosomes to which they are attached) apart to opposite ends of the cell. The force that causes the centrosomes to move towards the ends of the cell is still unknown, although there is a theory that suggests that the rapid assembly and breakdown of microtubules may cause this movement. At the end of anaphase the kinecticore microtubules all degrade.

Telophase (from the Greek τελος meaning "end") is a reversal of prophase and prometaphase events. It "cleans up" the after effects of mitosis. At telophase, the polar microtubules continue to lengthen, elongating the cell even more. Corresponding daughter chromosomes attach at opposite ends of the cell. A new nuclear membrane, using the membrane vesicles of the parent cell's old nuclear membrane, forms around each set of separated daughter chromosomes (though the membrane does not enclose the centrosomes) The nucleoli reappear, too. Both sets of chromosomes, now surrounded by new nuclei, begin to "relax" or decondense back into chromatin. Mitosis is complete, but cell division is not.