Question

The most dramatic period of the cell cycle is:
(a) M-phase
(b) G₁ phase
(c) S phase
(d) Interphase

Answer 1

Hint:Here the word ‘dramatic’ indicates about a phase of cell cycle in which major events take place.

Complete answer:Cell cycle means the cyclic sequence of events that take place to prepare the cell for its division into two new daughter cells. Cell cycle is broadly divided into two phases: 1) interphase 2) Mitotic phase or M-phase.

Interphase is further divided into three distinct stages, viz. G₁ phase, S phase and G₂ phase. In G₁ phase cells grow and prepare enzymes required for the next step.
In the S phase, DNA replication occurs.
In the G2 phase, the cell grows further and prepares for mitosis.

Mitosis or the mitotic phase is the most significant phase of the cell cycle. The major changes and events take place in this.
M-phase is divided into prophase, metaphase, anaphase and telophase. The chromosomes become dense (prophase) and get arranged into the equatorial plate (metaphase), then the chromatids get separated and move towards the poles of the cell (anaphase); upon reaching the poles, new nuclear envelope forms gradually (telophase) and then cytoplasm divides (cytokinesis). This is how two daughter cells are formed.

So, indeed, M-phase is the most dramatic phase of cell cycle.

Note: M-phase marks mitosis. For production of gametes, another set of cell division occurs, it is known as meiosis. Besides the above mentioned phases of the cell cycle there is another phase called G₀. It is a resting state of the cell.