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Mitosis and Meiosis Background
Animal cells reproduce based on the type of cells that are dividing. For example, somatic cells (bodily, non-sexual) depend on mitosis for reproduction while sexual cells (gametes such as sperm and ova) depend on meiosis for division. Both of these types of reproduction are similar, however they differ on how many cells are produced as well as some of the steps that are included in each of the processes.
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Mitosis and Cytokinesis in Animal Cells
Mitosis has five stages that are usually associated with it. The first is called interphase in which an animal cell prepares for reproduction by maturing and replicating its chromosomes. This step, even though it is not directly related to mitosis, is important for mitosis to begin.
The next step, prophase, starts with the chromatids beginning to separate, the formation of centrioles, and lastly the nuclear envelope starting to dissolve. Following prophase is metaphase, in which the chromatid turned chromosomes line up across the center of the cell forming a metaphase plate.
Next is anaphase, in which the spindles of the cell pull the chromatids apart to the ends of the cell. This allows the daughter and parent cells to have an equal amount of genetic material.
The last stage is telophase, and this is where cytokinesis in animals takes place. When an animal cell begins to divide, it is attributed to a structure called a contractile ring. The contractile ring tightens tighter and tighter by a protein called myosin and eventually makes a burrow called a "cleavage burrow." This process continues until the daughter and parent cells divide from one another.
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Meiosis and Cytokinesis in Animal Cells
Similar to mitosis, meiosis is the division of sexual gametes such as the sperm and ova cells. The stages of meiosis are similar to mitosis in that it has prophase, metaphase, anaphase, and telophase. Meiosis's stages in order are: prophase I, metaphase I, anaphase I, telophase I followed by meiosis II which ends with prophase II, metaphase II, anaphase II, and telophase II.
The main difference between mitosis and meiosis is that meiosis completes the process twice because it has to divide the cells first into two haploid cells in meiosis I and later divides into two more haploid cells in meiosis II. What's the difference between diploid and haploid cells?
It simply refers to the amount of genetic material that is passed on to the new cells. For example, haploid cells only receive half the chromosomes because these sex cells will receive the other half when they are fertilized. Diploid cells, on the other hand, receive roughly the full genetic material because they will never be fertilized (they are somatic after all).
So how does cytokinesis in animals happen in meiosis? Remarkably, it is the exact same as in mitosis; however, it happens two times, once in telophase I and next in telophase II. The only real difference is that cytokinesis is dividing haploid cells instead of diploid cells in mitosis. It is also important to remember that meiosis creates four haploid cells rather than mitosis which creates two diploid cells.
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- Crisholm, Rex. L. "Cytokinesis." http://www.biologyreference.com/Co-Dn/Cytokinesis.html
- Korgh, David. "Information to Genetics: Mitosis and Cytokinesis." http://wps.prenhall.com/esm_krogh_biology_3/17/4437/1135980.cw/index.html
- Muller, Michael. "Cell Division." http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect16.htm
- Javok. "Major Events in Meiosis." http://commons.wikimedia.org/wiki/File:MajorEventsInMeiosis_variant.svg
- Mysid. "Major Events in Mitosis." http://commons.wikimedia.org/wiki/File:Major_events_in_mitosis.svg