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How Mitosis Takes Place?


Posted Date: 20-May-2012  Last Updated:   Category: How things work    
Author: Member Level: Diamond    Points: 50


All of us have grown from a single cell to a multicellular organism due to the continuous mitotic cell division. This article provides all the information regarding the various phases of mitotic cell division. It also highlights its importance in our body, its occurrence as well as the history behind mitosis.



Introduction


Mitosis division is a major type of cell division in which the mother cell divides into two genetically as well as morphologically similar progeny cells. It is one of the most important cell division for the growth and development of the multicellular organisms. It is also known as duplication division and equational division because the number of chromosomes both in the mother cell as well as in the progeny cells remains the same. Mitosis cell division occurs through two steps, karyokinesis which is the division of the nucleus and the other is cytokinesis, which is the division of the cell cytoplasm and cell membrane. Before these two steps occur, the cell initially prepares itself for mitosis cell division. The cell undergoes various internal changes such as synthesizing of protein for the division, duplication of the number of chromosomes and many more. When the cell is fully prepared, then only mitosis cell division occurs.

History and occurrence of mitosis


Strasburger was the first biologist to study mitosis cell division. Later in the year 1879, Boveri and Flemming went deep into the theory studying the various phases of the cell division. It was Flemming who termed the cell division as mitosis. In 1887, Schneider explained the mitosis division with more details and he introduced the term 'karyokinesis' whereas Whiteman introduced cytokinesis.

Almost in every part of our body mitosis cell division takes place especially inside our bone marrows and on our skin. In plants mitosis mainly occurs in the meristematic regions of the plant that is on the shoot apex, root apex, nodes etc. Mitosis cell division plays a very important part in the growth of the embryo.

Karyokinesis in cell division


Karyokinesis refers to the division of the nucleus. Since the nuclear membrane disappears during karyokinesis and the chromatin fibers scatter in the cytoplasm of the cell, therefore karyokinesis is also known as indirect nuclear division. Karyokinesis occurs through four main phases but each phase is not very distinct, so a clear cut line between the phases can't be drawn properly.
Prophase: It is the first phase in karyokinesis and it is marked by the disappearing of the nuclear membrane of the nucleus. Some of the events occurring in this phase are,
  • The chromatin fibers condense to forms small rod like structures known as chromosomes.
  • Centrioles who got divided earlier move toward the two opposite ends of the cell and spindle fibers start forming from the centrioles.

  • Metaphase: It is the second phase of the cell division and it is marked by the complete disappearance of the nuclear membrane.
  • Spindle fibers from the centriole get attached to the kinetochores of the chromosomes.
  • All the chromosomes get themselves aligned on the equatorial region of the cell and it forms a plate like structure which is known as metaphase plate.

  • Anaphase It is the third phase of the cell division and also the fastest phase among the other three phases.
  • The centromeres of each chromosomes splits releasing the sister chromatids in the equatorial region.
  • The spindle fibers contract pulling the sister chromatids towards the two opposite ends of the cell.

  • Telophase: It is the last and the longest phase in the cell division. This phase lasts for usually 40 minutes.
  • The spindle fibres pull the chromatids to the opposite poles where these chromatids again changes to chromatin fibres and they start entangling with one another.
  • The nuclear membrane starts to reappear enclosing the newly formed nucleus and the centriole remains near the newly formed nucleus.

    Cytokinesis in cell division


    Cytokinesis refers to the division of the cell membrane and cytoplasm and it immediate follows karyokinesis. Cytokinesis in both animal and plant cells differs due to presence of rigid cell wall in plants cell. In animal cell, furrow is observed on the in the equatorial region on the both sides of the cell. These furrows deepen and ultimate meet at the centre of the cells dividing the mother cell into two newly formed daughter cells. In plant cell, cytokinesis occurs from the centre of the cell by the formation of new cell walls in the equatorial region of the cell. This new cell wall grows outward toward the outer cell wall and when it meets the outer cell wall, the two daughter cells get divided. The new cell wall grows to form a rigid cell wall providing shape to the newly formed cell.

    Importance of mitosis


    Mitosis cell division is very much essential as it plays a very significant role in the growth and development of multicellular organisms. Since it occurs on every parts of our body therefore its need is very much important for the survival. Some of the main importances of mitosis are,
  • Mitosis helps in the overall growth of an organism by increasing the number of cells in our body.
  • Mitosis helps in repairing of tissues and organs through regeneration of more and more new cells to replace the dead cell of our body.
  • Mitosis helps in maintaining the genetic material inside our cell through equal distribution of chromosomes between the newly formed cells and also maintaining the total number of chromosomes in the nucleus.
  • Mitosis plays an important role in maintaining the nucleo-cytoplasmic index of the cell. It ensures that the size of the nucleus and the cytoplasm are in the required ratio.
  • Mitosis cell division helps in forming smaller cells which are more efficient in the exchange of materials between the cell and the surrounding.

    Conclusion


    It takes around 1 hour or more for one complete mitosis cell division to occur. Everyday thousands of new cells are added in our body through this mitotic cell division and it plays an important role in both multicellular as well as unicellular organisms.


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