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Mitosis

Mitosis

There are four stages of mitosis, prophase, metaphase, anaphase, and telophase. In the past, prometaphase was considered a stage, but now that's just called "late prophase".

Prophase

In prophase, chromosomes coil up and condense. The chromosomes exist as two identical sister chromatids joined together. In addition, the mitotic spindle begins to form as microtubules grow out of the centrosomes. 

Sorry, this image is from Wikipedia, and I tried to take out the extra text.

Sorry, this image is from Wikipedia, and I tried to take out the extra text.

In late Prophase, or Prometaphase, the nuclear envelope breaks up, the spindle microtubules now connect to the chromosomes, and other microtubules.

Metaphase

Once again, sorry

Once again, sorry

In metaphase, the mitotic spindle is fully formed. The chromosomes line up in the middle of the cell, equidistant from both centrosomes.

Anaphase

In Anaphase, the sister chromatids of each chromosome separate. Each is now considered a daughter chromosome. Motor proteins at the centromeres move the daughter chromosomes along their microtubules toward the opposite sides of the cell. Microtubules containing chromosomes shorten, while microtubules not attached to chromosomes lengthen, pushing the poles farther apart.

Telophase and Cytokinesis

Telophase is the opposite of prophase. Nuclear envelopes form, the chromosomes uncoil, and the spindle disappears. Mitosis is now finished. Cytokinesis now occurs. In animals, a cleavage furrow pinches the cell in two, producing two daughter cells.  A cleavage furrow is an indentation at the equator of the cell. Microfilaments in the cytoplasm contract, deepening the furrow, and pinching teh cell into two. In plants, membrane-enclosed vesicles containing cell wall maetreial collect at the middle. The vesicles gradually fuse, forming a disk called the cell plate. That grows, and eventually it separates the plant cell into two.

David Witten

Recombinant DNA

The Cell Cycle