Cell Cycle

Cell cycle and cell division

The sequence of events by which a cell duplicates its genome synthesizes other cell contents, and eventually divides into two daughter cells is termed a cell cycle. It occurs in a coordinated manner under genetic control.

Phases of the cell cycle

A typical eukaryotic somatic cell has two main stages: long dividing interphase (I-phase) and a shorter nucleus dividing mitotic phase(M-phase) followed by cytokinesis.
Interphase is metabolically active stage and divided into the first gap phase (G1), synthesis phase (S phase), and second gap phase (G2 phase).
During the G1 phase, a cell can permanently stop division considered to be withdrawing itself from the cell cycle and enter the G0 or quiescent stage. Cells in the G0 phase remain metabolically active and start proliferation depending upon the requirement of the organism.
The length of the cycle depends on the nature of the cell and various external factors. The bacterial cell may divide once every 20 mins; in human cells, it lasts for 24 hours. Some specialized cells (nerve cells) never divide.

Figure: Cell cycle