Question

explain Karyokinesis and phases involve in it



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Answer 1

A) Karyokinesis: It is the division of nuclear material.

It occurs in four stages as follows:

i) Prophase (Gr. Pro – before, phases – appearance)

• It is the longest phase. During this phase the chromatin is organized into distinct chromosomes by

coiling or spiralization.

• The centrioles develop into asters and move towards the opposite poles of the cell to establish the

plane of cell division.

• Spindle apparatus begin to appear

• Nucleolus and Nuclear membrane disintegrate and disappear

• The chromosomes are set free in the cytoplasm.

ii) Metaphase (Meta – after, phase – appearance)

• Spindle fibres are completely formed

• The chromosome become short and thick with two distinct chromatids each

• All the chromosomes move towards the centre of the cell and arrange in the equatorial

plane, right angles to the position of asters to form metaphasic plate

• Chromosomes are attached to spindle fibres at their centromeres

Iii) Anaphase (ana – up, phases - appearance)

• The centromere of all the chromosomes undergo longitudinal splitting and the

chromatids of each chromosome separate to form daughter chromosomes

• The daughter chromosomes move toward the opposite poles from the equator by the activity of spindle fibres

Iv) Telophase (Telo – end, phases – appearance)

During this, the events of prophase will be reversed

• The daughter chromosomes reach the opposite poles

• The chromosomes undergo despiralization to form long, thin thread like structures called chromatin