Q.Distinguish cytokinesis from karyokinesis.
Karyokinesis is nuclear division while cytokinesis is cytoplasmic division; the M phase normally begins with the first and ends with the second.
When a cell divides, two separate things must be accomplished: the copied genetic material must be shared out into two nuclei, and the cell body itself must be split so that each nucleus finishes inside its own cell. These two events are given different names.
Karyokinesis is the division of the nucleus. It is the elaborate, step-by-step process in which the duplicated chromosomes are separated and gathered into two daughter nuclei. In mitosis it is described, for convenience, as passing through prophase, metaphase, anaphase and telophase. The M phase begins with this nuclear division.
Cytokinesis is the division of the cytoplasm. Once two nuclei have formed, the cell body pinches or partitions into two, so that each daughter nucleus is enclosed in its own separate cell. The M phase normally ends with cytokinesis, and only when it is complete is cell division genuinely over. During cytokinesis the organelles, such as mitochondria and plastids, are also distributed between the two daughter cells.
The two processes do not always go together. In some organisms karyokinesis takes place but is not followed by cytokinesis; repeated in this way, it produces a cell with many nuclei in a common cytoplasm — a multinucleate condition called a syncytium, as seen in the liquid endosperm of a coconut.
In short, karyokinesis divides the nucleus and cytokinesis divides the cytoplasm; the first precedes the second, and division is complete only once cytokinesis has occurred.
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