Amitosis

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Process of amitosis, where the cell divides as one cell via constriction, not as one cell replicating into two distinct cells.

Amitosis (a- + mitosis) is an obsolete term describing eukaryotic cell division different from mitosis that was supposed in the 19th century to exist. Compared to mitosis and cytokinesis, amitosis is a much simpler type of cell division, being the simplest. This is because this type of cell division is more direct rather than involving more in depth procedures or structures.

History[edit]

In the 1850s, Robert Remak described cell division but, because of methodological difficulties, could not observe condensed chromosomes, or chromatin. He presumed that division of the nucleolus was followed by splitting of the nucleus and then of the cell body. When Walther Flemming described mitosis and introduced the term in 1882, he called the previously described division "amitosis". With regard to it, he remarked that "it is a somewhat trying task to give an account of a subject of which the final outcome is so unsatisfactory". Future research provided an ever-growing amount of data on the mechanism and significance of mitosis, while "amitosis" was always associated with degenerating cells. It is a consensus opinion of today's cellular biologists that amitosis as a type of cell division does not exist, but many teaching and popular sources still present it. The microscopic picture of splitting nuclei and cell bodies of degenerating cells corresponds not to division but to apoptosis, a type of cell death.

Mechanisms[edit]

Amitosis, or "non-mitosis", is a four-stage process of a type of eukaryotic cell division differing from that of mitosis, the most common type of cell division. During the stages of this cell division, the nuclear membrane is not broken down as most scientists would have expected. (2) Amitosis involves a type of nuclear division that does not involve the condensation of chromatin into chromosomes and no spindle differentiation. This type of cell division is commonly seen in organisms such as amoebaeciliatessponges, tissues of vascular plantsarthropodsmammals, and dinoflagellates. (2) One of the major problems with amitosis is that it is an irreversible type of cell division, leaving daughter cells unable to reproduce. The mechanism of amitosis is different from mitosis due to the things previously mentioned. In 1967 Shen discovered that amitosis occurs in a pattern. Later in 1991, Maszewski determined that these cells divide symmetrically. (2) This contributes to the fact that daughter cells contain equally distributed amounts of chromatin. (1) It is a consensus opinion of today's cell biologists that amitosis as a type of cell division does not exist, but many teaching and popular sources still present it, although it is not a topic that receives much attention. Some biologists believe that the microscopic picture of splitting nuclei and cell bodies of degenerating cells corresponds not to division but to apoptosis, a type of cell death. Shows alternative methods of cell division as compared to amitosis, which includes a smaller variety of steps.

Differences[edit]

Shows alternative methods of cell division as compared to amitosis, which includes a smaller variety of steps.

Amitosis differs from other types of cell division in that it offers simpler mechanisms than cytokinesis and mitosis. Rather than one cell dividing into two completely new cells, the cell instead divides itself into two halves, maintaining its status as being of one cell, but representing itself in two separate entities. Amitosis occurs whenever mitosis cannot be performed. This is specifically possible whenever a cell reaches its adulthood, where replication is not necessary because of the newer, younger cells that have come into existence. The result of mitosis is is two separate daughter cells that contain two separate nuclei and form two distinct sets of organelles. Contrarily, amitosis derives from one cell and splits the nucleus and organelles between the newly formed daughter cells. This is done through cytoplasmic constriction.

References[edit]

  1. Jump up^ Wilson E.B., The cell in development and inheritance, MacMillan Co., London, 1897, accessed 14 November,2017
  2. Jump up^ Flemming W., Zellsubstanz, Kern und Zelltheilung, 1882
  3. Jump up^ Wilson E.B., The cell in development and inheritance, MacMillan Co., London, 1897, accessed 14 November,2017
  4. Amitosis, ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjOkDDPlmxWo6uco/wiki/Amitosis.html. (1) Vouilloud, Amelia A., et al. “Amitosis, Including Nucleolar Behaviour during Fragmentation, in Both Axial and Corticating Cells of Chara Contraria (Charales, Charophyta).” Phycologia, vol. 46, no. 2, Mar. 2007, pp. 178–186. Academic Search Complete, EBSCOhost, doi:10.2216/06-38.1. Accessed 2 Nov. 2017. (2)
  5. Ferguson FG, Palm J. 1976. Histologic characteristics of cells cultured from rat placental tissue. Am J Obstet Gynecol.124(4):415-20. 
  6. Kuhn EM, Therman E, Susman B. 1991. Amitosis and endocycles in early cultured mouse trophoblast. Placenta. 12(3):251-61. 
  7. Cotte C, Easty GC, Neville AM, Monaghan P. 1980. Preparation of highly purified cytotrophoblast from human placenta with subsequent modulation to form syncytiotrophoblast in monolayer cultures. In Vitro. 16(8):639-46.
  8. Difference between Mitosis and Amitosis. http://www.differencebetween.info/difference-between-mitosis-and-amitosis