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Mitosis is the process by which a cell divides into two identical daughter cells. It is a systematic cell division where the cells undergo step-wise changes. Mitosis is a highly complex and a well regulated activity. Before a cell undergoes mitosis, it stores energy necessary to drive the chemical processes that occur during mitosis. This phase is known as interphase of the cell cycle.

As at the end of mitosis two genetically identical daughter cells are formed, the parent cell makes a copy of each chromosome (complex of highly-coiled DNA that stores the genetic information required for proper cell functioning) during the interphase. At the end of mitosis, the daughter cells that are formed are known as clones.

There are four main stages in mitosis. They are prophase, metaphase, anaphase and telophase. At the end of these four stages a process called karyokinesis (nuclear division) is finished. Let us now consider each stage in detail.

1) Prophase:

The genetic material in the nucleus is usually in the form of chromatin (loosely bundled coil of DNA). During prophase the chromatin condenses into definite number of chromosomes. Each chromosome has a pair of sister chromatids bound together in the center by a structure called centromere.

Centrosomes are organelles present near the nucleus which are made of a pair of centrioles. Centrosomes are responsible for coordinating the cell's microtubules. The centrosomes along with the microtubules are known as spindle apparatus. During the prophase, two centrioles move towards opposite poles of the cell.

During prophase, the nuclear membrane and the nucleolus disappear.

Each chromosome forms a pair of complex protein structure, one attached to each chromatid called kinetochore, which ensures proper chromosome separation.

2) Metaphase:

The chromosomes undergo longitudinal division such that each centromere has four arms attached to it. This condition is called tetrid or bivalent condition. The spindle fibers attach themselves to the kinetochores of the chromosomes. Chromosomes now align themselves in the center of the cell.

3) Anaphase:

During anaphase, the spindle fibers begin to contract causing the chromosomes to break at the centromere. Thus half the centromere with two arms start moving towards the opposite poles.

4) Telophase:

This is the last phase in mitosis. This is just reversal of prophase. The nuclear membrane appears. Nucleolus is also formed. Chromatin is formed from the chromosomes. Thus in a single cell two nuclei will be present in a single cell at opposite poles.

At the end of mitosis cytokinesis occurs. This is the step where cytoplasm is divided by the formation of a furrow or cell plate, thus resulting in the formation of two identical daughter cells.

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