Mitosis is the division of a cell to form daughter cells in which each cell contains the same number of chromosomes as the parent cell. It occurs in somatic cell or both dy cell . Mitosis is a continuous process though it is considered in four stages .
1. Prophase
Chromosomes first appear as long thin thread like strictures . Chromosomes coil and become shorter and thick. Each chromosome is seen to be composed of 2 chromatids jeld together at a centromere. Centrioles held together at a centromere. Centrioles move to opposite poles of the cell and produce spindle fibers . Nucleolus shrink and finally disappears. Nyclear membrane breaks down to release the chromosomes.
2. Metaphase
Chromosomes are lined or arranged on the equator of the spindles with the chromatids of each chromosome oriented towards the opposite poles. Spindle fibers connect to the chromosomes at the centromeres.
3. Anaphase
Sister chromatids separate. once separated ,each chromatids is a chromosome. Spindle fibers shorten and pull towards opposite poles of the cell with the centromere in the lead.
4. Telophase
Chromosomes reach opposite poles of the cell and the spindle fibers disappear. Nuclear membrane and the nucleolus are reformed. In an animal cell,a construction or Cleavage furrow is formed along the equator. The constriction deepen and cut the cell into two daughter cells. In a plant cell ,a cell plate is formed along the equator to divide the cell into two.
Significance of mitosis
It maintains a constant chromosome number in somatic cells . It also leads to the growth of the organism . It ensures repairs and replacements of worn out and dead tissues . It is involved in asexual reproduction as cells of the parent divides in mitosis to provide cells which will form the offspring.
There are differences of how mitosis occurs in plant cells and animal cells.
In plant cells, the centrole is absent ,asters do not form , cell plates form to separate daughter cells and it occurs in meristems.
In an animal cell, the centriole is present , aster is formed , cell plates are not formed rather but there is a construction . And it occurs in all cells.
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