Question

Which state implies the exit of cells from the cell cycle?

• A. S
• B. G1
• C. G2
• D. G0

Hint:

The G0 phase is often referred to as the quiescent or resting phase.
Remember that while cells in G0 are non-dividing, they are highly metabolically active and performing their specific physiological functions.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The cell cycle consists of a series of tightly regulated phases that lead to cell division.
Cells can either actively progress through the cycle or exit into a quiescent, non-dividing state.

Step 2: Detailed Explanation:
The eukaryotic cell cycle is divided into Interphase (comprising G1, S, and G2 phases) and the M phase (mitosis).
During the G1 phase, cells monitor their environment and grow in size.
If environmental conditions are unfavorable, or if cells undergo terminal differentiation, they can exit the active cell cycle.
This exit occurs at a checkpoint in the late G1 phase, directing the cells into a specialized resting state called the G0 phase.
In the G0 phase, cells remain metabolically active but cease to divide or replicate their DNA.
Some cells, such as mature neurons and skeletal muscle cells, remain in G0 permanently.
Other cells, such as hepatocytes and lymphocytes, can re-enter the G1 phase of the cell cycle upon receiving appropriate cellular signals or growth factors.
The S phase is dedicated to DNA replication, and G2 is the pre-mitotic gap phase, neither of which represents an exit state.

Step 3: Final Answer:
The state that implies the exit of cells from the cell cycle is the G0 phase.