Statement I: During G0 phase of cell cycle the cell is metabolically inactive. Statement II: The centrosome undergoes duplication during S phase of interphase.

Statement I is incorrect but Statement II is correct

Both Statement I and Statement II are correct

Both Statement I and Statement II are incorrect.

Statement I is correct but Statement II is incorrect.

Quiescent Stage (G0)

ஓய்வு நிலை (G0)

NCERT Class 11 · Cell Cycle and Cell Division · 4 NEET questions

Most students assume cells are either dividing or dead. That is a fatal misconception. Many cells exit the cell cycle to enter G0, a state of metabolic precision, not inactivity.

The idea

Cells that do not undergo further division exit the G1 phase to enter the quiescent stage (G0). In this stage, cells remain metabolically active but do not proliferate. They continue to perform their specific physiological functions without entering the S-phase. This is a reversible state for some cells and permanent for others.

Why it matters

It allows cells to remain functional without dividing, preserving resources and maintaining tissue homeostasis in adult organisms.

NEET lens

NEET focuses on the 'metabolically active but non-proliferating' nature of G0. Remember: G0 is an exit from G1, not a part of the cell cycle proper. Do not confuse 'quiescent' with 'senescent'—they are biologically distinct.

Clinical significance

Neurons and cardiac muscle cells are classic examples of cells that enter a permanent G0 phase. When these cells are damaged, they cannot regenerate through mitosis, leading to permanent tissue loss. This is why myocardial infarction or spinal cord injuries result in irreversible damage.

Introduction

G0 (quiescent stage) is a state of cell cycle withdrawal where cells are alive and metabolically active but have exited the active cell cycle and are not preparing to divide.

Core concept

Types of G0: (1) Terminally differentiated cells — permanently in G0, will never divide again (neurons, cardiac muscle, skeletal muscle cells). (2) Reversibly quiescent cells — temporarily in G0, can re-enter cell cycle if stimulated (liver cells after partial hepatectomy, lymphocytes after antigen stimulation). Entry into G0: cells exit G1 (not G0 is a separate branch off G1). Most cells in adult body are in G0.

Go deeper

G0 is not simply arrested G1 — it is a distinct transcriptional and metabolic state with different gene expression patterns. Quiescent cells have lower RNA synthesis, reduced metabolic rate, and special maintenance programs to preserve viability for years.

From Class 10

Some cells stop dividing permanently. Others stop temporarily. Both types enter a special non-dividing state called G0.