Cell division


Cell division

Cell division is the process by which a parent cell divides into two or more daughter cells. Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort of cell division in prokaryotes is known as binary fission. In another type of cell division present only in eukaryotes, called meiosis, a cell is permanently transformed into a gamete and cannot divide again until fertilization. Right before the parent cell splits, it undergoes DNA replication.

For simple unicellular organisms[nb 1] such as the amoeba, one cell division is equivalent to reproduction-- an entire new organism is created. On a larger scale, mitotic cell division can create progeny from multicellular organisms, such as plants that grow from cuttings. Cell division also enables a sexually reproducing organisms to develop from the one-celled zygote, which itself was produced by cell division from gametes. And after growth, cell division allows for continual construction and repair of the organism.[1] A human being's body experiences about 10,000 trillion cell divisions in a lifetime.[2]

The primary concern of cell division is the maintenance of the original cell's genome. Before division can occur, the genomic information which is stored in chromosomes must be replicated, and the duplicated genome separated cleanly between cells. A great deal of cellular infrastructure is involved in keeping genomic information consistent between "generations".

Contents

Variants

Three types of cell division

Cells are classified into two categories: simple, non-nucleated prokaryotic cells, and complex, nucleated eukaryotic cells. By dint of their structural differences, eukaryotic and prokaryotic cells do not divide in the same way.

Furthermore, the pattern of cell division that transforms eukaryotic stem cells into gametes (sperm in males or ova in females) is different from that of eukaryote somatic (non-germ) cells.

Degradation

Multicellular organisms replace worn-out cells through cell division. In some animals, however, cell division eventually halts. In humans this occurs on average, after 52 divisions, known as the Hayflick limit. The cell is then referred to as senescent. Cells stop dividing because the telomeres, protective bits of DNA on the end of a chromosome required for replication, shorten with each copy, eventually being consumed, as described in the article on telomere shortening. Cancer cells, on the other hand, are not thought to degrade in this way, if at all. An enzyme called telomerase, present in large quantities in cancerous cells, rebuilds the telomeres, allowing division to continue indefinitely.

See also

Notes

  1. ^ Single cell organisms. See discussion within lead of the article on microorganism.

Other notes

  1. ^ Maton, Anthea; Hopkins, Jean Johnson, Susan LaHart, David, Quon Warner, David, Wright, Jill D (1997). Cells: Building Blocks of Life. New Jersey: Prentice Hall. pp. 70–74. ISBN 0-13423476-6. 
  2. ^ Quammen, David (April 2008). "Contagious cancer: The evolution of a killer". Harper's 316 (1895): 42. .

References

  1. Morgan DO. (2007) "The Cell Cycle: Principles of Control" London: New Science Press.
  2. J.M.Turner Fetus into Man (1978, 1989). Harvard University Press. ISBN 0-674-30692-9
  3. Cell division: binary fission and mitosis

They teach you cell division in the middle school.

External links


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Look at other dictionaries:

  • Cell division — Division Di*vi sion, n. [F. division, L. divisio, from dividere. See {Divide}.] 1. The act or process of diving anything into parts, or the state of being so divided; separation. [1913 Webster] I was overlooked in the division of the spoil.… …   The Collaborative International Dictionary of English

  • cell division — n the process by which cells multiply involving both nuclear and cytoplasmic division compare MEIOSIS, MITOSIS * * * reproduction of cells by division first of the chromosomes (karyokinesis) and then of the cytoplasm (cytokinesis). Cell division… …   Medical dictionary

  • Cell Division — Allgemeine Informationen Genre(s) Alternative Rock, Gothic Rock Gründung 1995 Website …   Deutsch Wikipedia

  • cell division — cell division. См. клеточное деление. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • cell division — reproduction of cells by division first of the chromosomes (karyokinesis) and then of the cytoplasm (cytokinesis). Cell division to produce more body (somatic) cells is by mitosis; cell division during the formation of gametes is by meiosis …   The new mediacal dictionary

  • cell division — ląstelės dalijimasis statusas T sritis augalininkystė apibrėžtis Vyksmas, kurio metu iš vienos ląstelės susidaro dvi. atitikmenys: angl. cell division; cell fission rus. деление клетки …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • cell division — cell′ divi sion n. cbl the division of a cell or cells in reproduction or growth • Etymology: 1880–85 …   From formal English to slang

  • cell division — Formation of two or more daughter cells from a single parent cell. The nucleus divides first, followed by the formation of a cell membrane between the daughter nuclei. Division of somatic cells is termed mitosis; egg and sperm precursors are… …   Glossary of Biotechnology

  • cell division — The separation of one cell into two daughter cells, involving both nuclear division (mitosis) and subsequent cytoplasmic division (cytokinesis) …   Dictionary of molecular biology

  • cell division — noun the process in reproduction and growth by which a cell divides to form daughter cells • Syn: ↑cellular division • Hypernyms: ↑organic process, ↑biological process • Hyponyms: ↑amitosis, ↑cleavage, ↑ …   Useful english dictionary


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