Question

Explain the mitosis in detail with the help of diagram.

Answer 1

• Mitotic division is also called somatic division or equational division.
• It occurs in two steps- karyokinesis ( nuclear division), cytokinesis (a division of cytoplasm).
• Four stages of karyokinesis are:-

1) Prophase:-

• Longest phase
• Chromatin fibres condense to form elongated chromosomes.
• Centrosome divides and daughter centrosome begin to move away from each other.
• Chromosomes shorten, centrosomes develop asters and develop spindle fibres.
• Nucleolus degenerates and nuclear envelope breaks.

2) Metaphase:-

• Chromosomes are shortest and thickest at this stage.
• Each chromosome gets attached to 2 spindle fibres from each pole in the region of kinetochores.
• The kinetochore fibres contract and bring chromosomes over the equator.
• The apparent plate formed is called equatorial or metaphase plate.

3) Anaphase:-

• Shortest duration phase.
• Anaphase-promoting complex develops.
• It degenerates protein binding the 2 chromatids in the region of the centromere.
• As a result centromere of each chromosome divides.
• Chromosomes move to the poles with centromeres projecting towards the poles and limbs trailing behind.

4) Telophase:-

• Stage of reconstitution of nuclei.
• Chromosomes uncoil, elongate, lose their stainability and form chromatin fibres.
• Nucleolar organisers form nucleoli in one or more pairs of chromosomes.
• Nucleoplasm and nuclear membrane appear forming 2 daughter nuclei.
• Cytokinesis:- It begins towards the middle of anaphase and completed simultaneously with completion of telophase.
• It brings the equitable distribution of cells organelles.