Mitosis
From Simple English Wikipedia, the free encyclopedia
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 with 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 describe what kind of change the cell is going through. The phases are Interphase, Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis. Some may consider prometaphase as part of the phases but most believe it is part of metaphase and some of the end of prophase. Each phase is important to mitosis.
[edit] Prophase
During prophase, the cell's genetic material (DNA)or deoxyribonucleic acid along wih ribonucleic acid (RNA), 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 happens 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 proteins.
[edit] Cytokinesis
During cytokinesis, the cell physically splits. The cleavage furrow, which is the pinch caused by the ring of proteins, pinches off completely, closing off the cell. The cell now has reproduced itself successfully. After cytokinesis, the cell goes back into interphase, where the cycle is repeated. What would happen if cytokinesis occurred without mitosis?
