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8.2.1.6. More on mitosis

Cell division abnormalities

Sometimes the cell cycle does not occur in the way we have seen. Some exceptions are:

  • The plasmodium. They are polynucleated cells in which karyokinesis has occurred several times but not cytokinesis.
  • The endomitosis. It can also be the case that the DNA is replicated, several times, without the cell dividing, so that the cell has a chromosomal endowment higher than normal. These are polyploid cells.
  • The amitosis. It occurs when, after karyokinesis, the chromosomes have not been distributed equally. It is not a reproductive method, but a pathology.

Types of cell division

  • Bipartition or binary division. As we have seen, it occurs when two identical daughter cells originate from the mother cell. Karyokinesis occurs first and then, in animal cells, the cytoplasm is strangled, until cytokinesis occursIn plant cells, this process is carried out by septification. 
  • Pluripartition or multiple division. The nucleus divides several times and cytokinesis occurs , resulting in more than two daughter cells from the original cell.
  • Budding. A bulge called a yolk occurs in the cytoplasm. The nucleus of the progenitor cell divides and one of the daughter nuclei passes into the yolk. Then, a membrane separates the two nuclei, leaving a daughter cell much smaller than the parent cell.
  • Sporulation. The progenitor cell surrounds itself with a covering that insulates it from the outside. The nucleus then divides several times without cytokinesis, and each daughter nucleus is surrounded by cytoplasm, plasma membrane, and envelope. When the covering of the mother cell is broken, these daughter cells or spores will be released, and when they find a suitable environment they will uncrypt to develop their functions, grow and reproduce.

Biological importance of mitosis

The mitosis is the way they multicellular organisms reproduce asexually. The descendants are genetically the same as the parent.

Multicellular organisms use mitosis to increase cell numbers, grow, and regenerate cellstissues, and organs.

The purpose of mitosis is to preserve the genetic material of the cell and distribute it between its two daughter cells. Thus, the two resulting cells are the same as the mother.


         

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Biology and Geology teaching materials for Compulsory Secondary Education (ESO) and Baccalaureate students.