Meiosis and mitosis are both processes of cell division. There are many similarities between meiosis and mitosis, but there are also important differences. Both processes result in the formation of new cells, and both involve a single duplication of DNA. Both processes occur in stages, and the events that take place during these stages are similar.
However, the purposes of meiosis and mitosis differ in that mitosis is generally responsible for the reproduction of somatic cells. A somatic cell is any cell in the body of a multicellular organism that is not a germ-line cell. Mitosis is important for growth, maintenance, and the repair of tissues and takes place in most cells of an organism. In mammals, old skin cells, muscle cells, intestinal cells, and (immature) blood cells, among many others, are all replaced through mitosis. In plants, mitosis enables growth in height and width and an increase in root, stem, and leaf mass.
Meiosis, in contrast, is generally responsible for the formation of gametes; a gamete is a sex cell of a sexually reproducing organism, with a haploid set of chromosomes. A gamete is used only in sexual reproduction. Female gametes are called ova, or eggs, and male gametes are called sperm. In both female and male organisms, meiosis occurs only in germ-line cells. A germ-line cell is a gamete or any of the precursor cells that divide to produce gametes. The organs where germ-line cells exist in a mature animal are the ovaries in females and the testes in males. These are the sites of gametogenesis, which is the production of gametes through the process of meiosis.Organisms that reproduce by asexual reproduction—a form of reproduction that does not involve fusion of gametes, producing offspring genetically identical to the parent—do so without the use of gametes and do not have cells that undergo meiosis. Their cells do, however, carry out mitosis.