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Mitosis and meiosis are both processes of cell division, by which one cell divides into daughter cells. The terms specifically refer to the stages of cell division in which the cell's chromosomes, which contain copies of the organism's genetic information, divide. Mitosis and meiosis differ in a variety of ways, including the number of daughter cells eventually produced and the number of copies of genetic information contained in each daughter cell. In mitosis, for instance, a parent cell divides to form two daughter cells that contain two copies of each of the parent cell's chromosomes. In meiosis, on the other hand, one parent cell divides twice to form four daughter cells that contain only one copy of each chromosome.
These differences in the outcomes of mitosis and meiosis are directly linked to the functions of the two forms of cell division. Mitosis, by which a single cell divides into two identical cells, is simply used for growth, development, and repair. One skin cell, for instance, will divide to form two identical skin cells. Meiosis, on the other hand, produces gametes, such as egg and sperm cells in animals or spores in fungi. The single chromosomal copy in each of the meiotic daughter cells contains a mix of paternal and maternal genetic information, which ensures that the offspring will not be genetically identical to either parent.
The steps that occur during the processes of meiosis and mitosis also differ somewhat. The differences primarily occur because two divisions occur during meiosis while only one occurs during meiosis, though there are other differences as well. It is important to note that the daughter cells resulting from mitosis are identical genetic matches to the parent cell while those that result from meiosis are not. An organism's genetic integrity depends on consistent cell division that does not alter the genetic code. Offspring, however, are often better equipped to survive if they receive a mix of traits that is not a genetic replica of either parent.
One major difference between mitosis and meiosis that can contribute significantly to genetic diversity in offspring is referred to as "crossing over" or "chromosomal crossover." Crossing over occurs only in meiosis. Homologous chromosomes can physically "swap" chromosomal segments, thereby ensuring that the information contained on the single chromosome in a meiosis daughter cell is genetically distinct from the information contained in the parent organism's genome.