Question

The correct sequence of adult cell cycle phases is

• A. S-M-G2-G1
• B. G1-G2-S-M
• C. G1-M-G2-S
• D. G1-S-G2-M

Hint:

Cell cycle order: G1 = Growth S = DNA synthesis G2 = Preparation M = Cell division

Answer 1

The Correct Option is D

Concept: Cell cycle is the sequence of events by which a cell grows, replicates DNA and divides into daughter cells. The adult cell cycle is divided into interphase and mitotic phase. Interphase includes G1 phase, S phase and G2 phase. This is followed by M phase where actual cell division occurs. Thus sequence must follow exact chronological order.

Step 1: Understand G1 phase.
G1 phase is first growth phase. Cell synthesizes proteins and increases size. Metabolic activity remains high. Thus cycle begins with G1.

Step 2: Understand S phase.
S phase stands for synthesis phase. DNA replication occurs during this phase. Chromosomes duplicate preparing cell for division. Thus S phase follows G1.

Step 3: Understand G2 phase.
G2 phase is second growth phase. Cell synthesizes proteins required for mitosis. Cell prepares final machinery for division. Hence G2 comes after S phase.

Step 4: Understand M phase.
M phase means mitotic division. Actual separation into daughter cells occurs here. Thus final sequence becomes \[ G1\rightarrow S\rightarrow G2\rightarrow M \] Hence answer is \[ \boxed{\text{Option (4)}} \]