Mitosis or Equational Division

Mitosis is a kind of cell division that occurs in somatic cell of the body. It produces two daughter cells in each division. And those daughter cells have the same number of chromosomes as in mother cells i.e a haploid mother cell (n) will produce two haploid daughter cells (n) and a diploid mother cell (2n) will produce two diploid (2n) daughter cells.

Where does mitosis occur?

As mentioned above mitosis occurs in those cells, where the ploidy level needs to be constant both in mother and daughter cells. This type of cells include:

  • Somatic cells of lower and higher organisms.
  • Meristematic cells of the plant body such as apical meristem of root, stem, procambium tissues etc.

In meiosis, there are two process which occurs periodically:
1. Karyokinesis
2. Cytokinesis

Karyokinesis (Division of nucleus)

There are 5 phases

A) Prophase
It lasts about 50 minutes.
There are 3 sub-phases:

Fig: Prophase

a) Early Prophase
1.The cells become almost round and the cytoplasm becomes viscous.
2.Dehydration of chromosomes.
3.Microtubules are arranged in spindle fibre.

b) Middle Prophase
1.Chromosomes further get shorter and thicker.
2.Nucleolus progressively becomes smaller and finally disappear.
3.Nuclear membrane begins to break down.

c) Late Prophae
1.Nuclear membrane breaks completely and releasing the chromosomes.
2.Spindles get their proper shape and size.
3.Spindles and centriole pairs take position to the poles.

B) Pro-metaphase

1.Spindles get attached with centromeres.
2.Disappearance of nuclear membrane and nucleolus.
3.Chromosomes are moving to and fro.

C) Metaphase
It lasts only 2-10 minutes
1. The spindles occupies the region of nucleus.
2. The chromosomes move to the equatorial region of the cell.
3. Each chromosome is splitted longitudinally except centromere.
4. Chromosomes are in maximum thickness and short.
5. Chromosomes get settled down at equatorial region.

Fig:Metaphase

D) Anaphase
1. Finally the centrosomes are splitted by the contraction of spindle fibre coming from two opposite poles.
2. Due to continuous contraction of spindle,one set of daughter chromosomes move to one pole and othet set to another pole.
3. On the basis of the position of centromere different chromosomes show different shape.

Fig:Anaphase

E) Telophase
1. Chromosomes become uncoiled.
2. Hydration of chromosomes.
3. Appearance of nuclear membrane and nucleolus.
4. Chromarids become invisible.

Fig:Telophase

Cytokinesis (Division of cytoplasm)

Along with cytoplasm cellular organelles equally divided. In some cases, cell plate between two newly formed cells is appeared.

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