The cell division cycle is responsible for increasing and maintaining cell number and size. This cycle is an essential feature of living organisms. There are four phases of cell division mitotic phase (M phase), growth phase 1 (G1), growth phase 2 (G2), and synthesis phase (S). One phase of the cell cycle ends, and the other starts; this is named a phase transition—a unidirectional alteration in the cell cycle phases. During G1, G2, and S phase cell grows and during the M phase cell divides. There are two models of cell reproduction as the clock model and the domino model. The domino model implies that cell division phases must occur in a distinct order and at a definite time. The domino model recommends that the cell cycle events are independent, while the clock model shows that the effectiveness of mitosis entrance was not persuaded by other actions.
