Mitosis

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Mitosis is the time in a cell's life when it makes more cells by splitting in half. Before mitosis, the cell creates an identical set of genetic information. The duplicated genetic information then winds up into a visible object called a chromosome. A chromosome is made up of two chromatids joined at the centromere. Mitosis happens in all cells of the human body exept for two exceptions: ova in females and sperm in males. These two cells go through a different reproduction method called meiosis.

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[edit] Phases of Mitosis

There are six phases of mitosis. Each phase is used to discribe what kind of change the cell is going through. The phases are Prophase, Prometaphase, Metaphase, Anaphase, Telophase, and Cytokinesis. Each phase is crucial to mitosis.

[edit] Prophase

During prophase, the cell's genetic material (DNA) coils up into bunches called chromosomes. The genetic material has already been duplicated during interphase, so there are double the amount of chromosomes in a normal cell in it. For example, a human cell normally has 23 pairs of chromosomes, but during early mitosis there are 46 pairs.

[edit] Prometaphase

During prometaphase, the nuclear membrane breaks down and the chromosomes are released. Spindle fibers form and attach themselves to the chromosomes' centromeres. The chromosomes are prepared for division.

[edit] Metaphase

During metaphase, the chromosomes are pulled by the spindle fibers into place. The chromosomes line up on the cells equator, or center line, and are prepared for division once again.

[edit] Anaphase

During anaphase, the chromosomes are pulled apart by the spindle fibers and pulled to opposite sides of the cell. This phase is short, as it only when the chromosomes are actually dividing.

[edit] Telophase

Telophase is for the most part a reveral of what happens in prophase and prometaphase. The spindle fibers break down, the nuclear membrane reforms, and the chromosomes (now called chromatids after they are separated) unwind into their original genetic material. The cell's cytoplasm is starting to be pinched at the center by a ring of protiens.

[edit] Cytokinesis

During cytokinesis, the cell physically splits. The cleavage furrow, which is the pinch caused by the ring of protiens, pinches off completely, closing off the cell. The cell now has reproduced itself sucessfully. After cytokinesis, the cell goes back into interphase, where the cycle is repeated.