– In mitosis, Nucleus and chromosomes both divide only once and thus the same chromosome number is maintained in new cells.

– Thus mitosis involves the division of nucleus which results in daughter nuclei with same genetic constitution as that of parent nucleus.

– Mitosis is found in somatic cells in both plants and animals. Mitosis can be divided into five phases:-

1. Prophase

– It is longest mitotic stage each chromosome is made up of two chromatids.

– In early stage of prophase both the chromatids of each chromosome are coiled about each other relationally they can’t be easily separated ( i.e, they are actually twisted together ).

– The nucleolus disappears at end of prophase and the nuclear envelope is also broken down, which disappears into cytoplasm as elements of endoplasmic reticulum.

2. Metakinesis ( pro-metaphase )

– It is the stage which occurs before metaphase.

– In this stage Chromosomes move towards the central region of cell.

– In both plant and animal cell, regardless of its origin, the spindle fibre apparatus is seen.

– The movement of chromosomes towards center of cell and their axis of orientation are governed partly by fibres.

– The spindle fibre attaches to a centromere of chromosome.

3. Metaphase

– At this stage the spindle is fully developed, the chromosomes are arranged at equatorial plane and the nuclear envelope and nucleoli are fully disappeared.

– They could lie in equatorial plane of cell, centromeres divide and each chromatid, now a single chromosome, moves to align itself on equatorial plate of metaphase.

4. Anaphase

– It is the shortest of all stages in mitotic cycle.

– This begins when the chromatid of ech chromosome start moving a part in opposite directions.

– In this way the chromatids are now identically divided between two poles and Chromosome number remains constant.

5. Telophase

– When the chromatids have reached the opposite poles, they form a close group at each poles.

– The chromatids at each pole are now known as daughter chromosomes.

– During this phase Nuclear membrane and nucleoli re-appear and surround the chromosomes.

– The daughter Chromosomes loosen their coils and lose their stain ability.

– Each chromatid gives rise to Two Chromonemata attached subterminally by centromere and thus ultimately the chromatids go back to prophase condition and form the reticulum.

Cytokinesis

– The process in animal cell usually begins at about the late Anaphase (or) early Telophase.

– During this phase the division of cytoplasm appears.

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