Like mitosis, meiosis is a formof eukaryotic cell division. However, these two processes distribute geneticmaterial among the resulting daughter cells in very different ways. Mitosiscreates two identical daughter cells that each contain the same number ofchromosomes as their parent cell. In contrast, meiosis gives rise to fourunique daughter cells, each of which has half the number of chromosomes as the parentcell. Because meiosis creates cells that are destined to become gametes (or reproductive cells), thisreduction in chromosome number is critical — without it, the union of twogametes during fertilization would result in offspring with twice the normalnumber of chromosomes!
Apart from this reduction in chromosome number, meiosis differs from mitosisin yet another way. Specifically, meiosis creates new combinations of geneticmaterial in each of the four daughter cells. These new combinations result fromthe exchange of DNA between paired chromosomes. Such exchange means that thegametes produced through meiosis exhibit an amazing range of genetic variation.
Finally, unlike mitosis, meiosis involves two rounds of nuclear division, notjust one. Despite this fact, many of the other events of meiosis are similar tothose that occur in mitosis. For example, prior to undergoing meiosis, a cellgoes through an interphase period in which it grows, replicates its chromosomes,and checks all of its systems to ensure that it is ready to divide. Likemitosis, meiosis also has distinct stages called prophase, metaphase, anaphase,and telophase. A key difference, however, is that during meiosis, each of thesephases occurs twice — once during the first round of division, called meiosisI, and again during the second round of division, called meiosis II.
