Mitosis is CELL DIVISION in eukaryotice (plant or animal) cells.
Why is mitosis important?
-By making new cells through mitosis, dead cells are replaced
-Through mitosis, living things are able to become multicellular organisms (this is how we went from being 1 cell to multiple cells).
--When mitosis goes wrong, cells can divide uncontrollably and a person can get cancer.
Below is a diagram of the phases of mitosis:
INTERPHASE is the stage before mitosis. This is just when the cell is growing (in G1 and G2 phases), and DNA is replicating. No cell division occurs at this point. You will notice that the nucleus is in tact, and the DNA is found in strands.
1. The first real mitosis phase is PROPHASE. In this phase, the nuclear envelope breaks up, or dissolves, the DNA is in chromosomes and (those X-like structures), the spindle fibers begin to form.
2. METAPHASE comes next. The chromosomes line up in the middle of the cell, along the metaphase plate, and are attached to the spindle fibers.Note that the spindle fibers are attached to centrioles in the poles.
3. ANAPHASE: The spindle fibers pull apart the chromosomes to 2 separate sister chromatids. Now, you will find the sister chromatids separated along the 2 poles of the cell.
4. The last phase of mitosis is TELOPHASE. In this phase, the nuclear envelope re-forms and 2 nuclei are found in the long, extended cell.
After mitosis comes CYTOKINESIS. This is when the cytoplasm divide in 2, and 2 separate cells are formed.
-Cytokinesis is slightly different in plants and animals. In plants, a cell wall is formed along the middle of the cell, and then 2 cells are formed. In animals, the cytoplasm pinches in, and then 2 cells are formed.
Here is a diagram of animal cell cytokinesis (note the cleavage furrow that forms):
Here is a diagram of plant cell cytokinesis (note the cell wall that forms in the middle of the cell):
Here is an animation that takes you through all of the stages..
http://www.cellsalive.com/mitosis.htm
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