Mitosis

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Mitosis in an ainimal cell.

Mitosis is a pairt o the cell cycle in which chromosomes in a cell nucleus are separatit intae twa identical sets o chromosomes, each in its ain nucleus. In general, mitosis (diveesion o the nucleus) is eften follaed bi cytokinesis, which divides the cytoplasm, organelles an cell membrane into twa new cells containin roughly equal shares o these cellular components.[1] Mitosis an cytokinesis thegither define the mitotic (M) phase o an ainimal cell cycle—the diveesion o the mither cell intae twa dochter cells genetically identical tae ilk ither.

The process o mitosis is dividit intae stages correspondin tae the completion o ane set o activities an the start o the next. Thir stages are prophase, prometaphase, metaphase, anaphase, an telophase. In mitosis, the chromosomes, that hae awready duplicatit, condense an attach tae spindle feebres that pull ane copy o ilk chromosome tae opposite sides o the cell.[2] The result is twa genetically identical dochter nuclei. The rest o the cell mey then conteena tae divide bi cytokinesis tae produce twa dochter cells.[3] Producin three or mair dochter cells insteid o normal twa is a mitotic error cried tripolar mitosis or multipolar mitosis (direct cell triplication / multiplication).[4] Ither errors in mitosis can induce apoptosis (programmed cell daith) or cause mutations. Certaint teeps o cancer can arise frae sic mutations.[5]

Mitosis occurs anerly in eukaryotic cells. Prokaryotic cells, that lack a nucleus, divide bi a different process called binar fission. Mitosis varies atween organisms.[6] For ensaumple, ainimal cells unnergae an "appen" mitosis, whaur the nuclear envelope braks doun afore the chromosomes separate, whauras fungi unnergae a "closed" mitosis, whaur chromosomes divide within an intact cell nucleus.[7] Maist ainimal cells unbergae a shape chynge, kent as mitotic cell roondin, tae adopt a near spherical morphology at the stairt o mitosis. Maist human cells are produced bi mitotic cell diveesion. Important exceptions include the gametessperm an egg cells – that are produced bi meiosis.

References[eedit | eedit soorce]

  1. Carter, J. Stein (2014-01-14). "Mitosis". biology.clc.uc.edu. 
  2. "Cell Division: Stages of Mitosis | Learn Science at Scitable". www.nature.com. Archived frae the oreeginal on 2015-11-14. Retrieved 2015-11-16. 
  3. Maton A, Hopkins JJ, LaHart S, Quon Warner D, Wright M, Jill D (1997). Cells: Building Blocks of Life. New Jersey: Prentice Hall. pp. 70–4. ISBN 0-13-423476-6. 
  4. Kalatova B, Jesenska R, Hlinka D, Dudas M (January 2015). "Tripolar mitosis in human cells and embryos: occurrence, pathophysiology and medical implications". Acta Histochemica. 117 (1): 111–25. doi:10.1016/j.acthis.2014.11.009. PMID 25554607. 
  5. Kops GJ, Weaver BA, Cleveland DW (October 2005). "On the road to cancer: aneuploidy and the mitotic checkpoint". Nature Reviews. Cancer. 5 (10): 773–85. doi:10.1038/nrc1714. PMID 16195750. 
  6. Raikov, IB (1994). "The diversity of forms of mitosis in protozoa: A comparative review". European Journal of Protistology. 30 (3): 253–69. doi:10.1016/S0932-4739(11)80072-6. 
  7. De Souza CP, Osmani SA (September 2007). "Mitosis, not just open or closed". Eukaryotic Cell. 6 (9): 1521–7. doi:10.1128/EC.00178-07. PMC 2043359Freely accessible. PMID 17660363.