Notes On Cytokinesis and the Significance of Mitosis - CBSE Class 11 Biology
M phase or the mitosis phase of the cell cycle is the mitosis or karyokinesis along with cytokinesis. Mitosis results in the segregation of duplicated chromosomes into two daughter nuclei and is followed by the division of cytoplasm, that is, cytokinesis, to produce two daughter cells.

In animals, cytokinesis is initiated by the formation of a furrow in the plasma membrane, which gradually deepens dividing the cytoplasm into two. Plant cells form a cell-plate in the centre of the cell, which gradually grows outward to meet the existing lateral cell walls. At the same time, organelles like plastids and mitochondria are equally distributed between the daughter cells.
 
In some organisms, karyokinesis is not followed by cytokinesis, which results in the formation of a syncytium, a cell with multiple nuclei. Such syncytium is found in the early embryo of drosophila and the liquid endosperm of coconut. Daughter cells inherit the same diploid number of chromosomes as in the mother cell through mitosis. It is generally seen in diploid cells, but mitosis occurs in haploid cells too in case of bryophytes and honey bees. Moreover, mitosis results in the formation of new cells, which replace dead cells. For example, blood cells and cells in the upper layers of the epidermis in the skin and the lining of the gut are continually replaced. In plants, namely the apical and the lateral cambium, divide actively by mitosis, leading to the continuous growth of the plant.

Summary

M phase or the mitosis phase of the cell cycle is the mitosis or karyokinesis along with cytokinesis. Mitosis results in the segregation of duplicated chromosomes into two daughter nuclei and is followed by the division of cytoplasm, that is, cytokinesis, to produce two daughter cells.

In animals, cytokinesis is initiated by the formation of a furrow in the plasma membrane, which gradually deepens dividing the cytoplasm into two. Plant cells form a cell-plate in the centre of the cell, which gradually grows outward to meet the existing lateral cell walls. At the same time, organelles like plastids and mitochondria are equally distributed between the daughter cells.
 
In some organisms, karyokinesis is not followed by cytokinesis, which results in the formation of a syncytium, a cell with multiple nuclei. Such syncytium is found in the early embryo of drosophila and the liquid endosperm of coconut. Daughter cells inherit the same diploid number of chromosomes as in the mother cell through mitosis. It is generally seen in diploid cells, but mitosis occurs in haploid cells too in case of bryophytes and honey bees. Moreover, mitosis results in the formation of new cells, which replace dead cells. For example, blood cells and cells in the upper layers of the epidermis in the skin and the lining of the gut are continually replaced. In plants, namely the apical and the lateral cambium, divide actively by mitosis, leading to the continuous growth of the plant.

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