by Mary Pagay

Created on: November 10, 2006   Last Updated: May 02, 2007

Mitosis and meiosis are similar processes in different body cells. Both processes involve the division of cells - one into two, two into four, four into eight. But, mitosis takes place in all cells of the body that are NOT related to reproduction and results in the same number of nuclei as the parent cell. Meiosis, on the other hand takes place in the reproductive cells and involve the division of cells and chromosomes resulting in twice the number of nuclei and half the number of chromosomes in each of those nuclei.

To be more specific: according to the Anatomy & Phsyiology book written by Rod Seeley, et.al. (1992, p. 94): "Mitosis is the division of the nucleus into two nuclei, each of which has the same amount and type of DNA as the original nucleus ... The formation of all the body's cells except for sex cells occurs by mitosis. Sex cells are formed by meiosis, a process in which the nucleus undergoes two divisions resulting in four nuclei, each containing half as many chromosomes as the parent cell."

Now, you may wonder why the sex cells end up with half the number of chromosomes. Well, the answer is really a lot easier than it seems. Sex cells are meant to be combined - one from the male and one from the female - to form a baby. Male cells are referred to as "spermatozoa" and female sex cells are known as "oocytes." Generically, sex cells are often referred to as "gametes." Just as a male and a female form a physical union to create a child, so do the gametes. The spermatazoan cell, with half the number of body cell chromosomes (a "haploid" number), forms a physical union with the female cell (also with half the number of body cell chromosomes). When the male and female gametes complete their union, through the process of meiosis, the resulting baby cell ends up with ... you guessed it - the FULL number of body chromosomes (half from the father, half from the mother).

Cells that results from mitosis are identical to the single, original parent cell. Very much like a clone. However, cells that result from meiotic division are genetically a combination of the two parent cells where the chromosomes are mixed and matched between the chromosomes of male and females gametes. In that way, the baby cell is similar to both parents, but identical to neither.

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