91Ó°ÊÓ

DNA in a eukaryotic cell is associated with various proteins to form chromatin. Just before cell division, chromatin becomes organized into compact structures called chromosomes.

As chromatin is highly condensed during cell division, the chromosomes can be easily seen and described using light microscopy. Each chromatin fiber contains one DNA molecule.

The cell cycle is a series of episodes that occur in a cell as it grows and divides and eventually gives rise to two new cells. It is the period between the beginning of one cell division and the beginning of the next.

Interphase, mitosis, and cytokinesis are the cell cycle stages that lead to the division of cells.

The cell grows, develops, and performs its assigned functions during interphase. During interphase, the chromatin is not condensed and is scattered throughout the nucleus.

Mitosis divides the cells into two through the following five stages:

• Prophase: Thecondensation of chromatin begins, and the nucleolus disappears.The chromatins are visible as chromosomes in this phase.
• Prometaphase:The nuclear membrane disappears during this phase. The chromosomes get attached to the mitotic spindle through the kinetochore.
• Metaphase:The centromeres of the chromosomes get aligned across the equatorial plane of the cell.
• Anaphase: Thechromatids split and move to the opposite poles of the cell.
• Telophase:Each chromatid reaches the poles of the cell, and the nuclear membrane reappears. The mitotic spindle disintegrates in this phase.

The division of the nucleus is followed by cytokinesis.

When the chromosomes reach the cell poles, the cytoplasm divides to complete the formation of two new daughter cells. This process is called cytokinesis which divides the cell into two components of chromosomes.