Given graph P,Q,R and S show four stages of cell cycle i.e., G1,S,G2 and M but in random order. Identify the stages and match the activities of the cell (I) Taxol treatment, which prevents microtubule depolymerization, arrests the cell at this stage. (II) With a mitogen treatment such as an epidermal growth factor and arrested cell at this stage proceed to the next stage of the cell cycle. (III) The cell cycle checkpoint at this stage confirms that DNA duplication is complete before the cell proceeds to the next stage.

Medical

Biology

Cell Organization

Mitosis

Meiosis

Question

Given graph P,Q,R and S show four stages of cell cycle i.e., G₁,S,G₂ and M but in random order. Identify the stages and match the activities of the cell
(I) Taxol treatment, which prevents microtubule depolymerization, arrests the cell at this stage.
(II) With a mitogen treatment such as an epidermal growth factor and arrested cell at this stage proceed to the next stage of the cell cycle.
(III) The cell cycle checkpoint at this stage confirms that DNA duplication is complete before the cell proceeds to the next stage.

I - P,II - Q,III - R

$I - Q,II - S,III - R$

$I - R,II - Q,III - S$

$I - p,II - S,III - Q$

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This question involves identifying stages of the cell cycle (G₁, S, G₂, M) from graphs showing DNA content per cell and matching them with specific cellular activities or treatments.

The cell cycle consists of:

G₁ phase: Cell growth before DNA replication. DNA content is 2C (diploid).
S phase: DNA synthesis (replication). DNA content increases from 2C to 4C.
G₂ phase: Preparation for mitosis. DNA content is 4C.
M phase: Mitosis (cell division). DNA content decreases from 4C to 2C after cytokinesis.

Analyzing the graphs (P, Q, R, S) based on DNA content:

Graph with lowest DNA content (2C): G₁ phase
Graph with intermediate DNA content (between 2C-4C): S phase
Graph with highest DNA content (4C): G₂ or M phase (before division)
Graph showing decrease from 4C to 2C: M phase (during division)

Now let's analyze the three statements:

(I) Taxol treatment: Taxol prevents microtubule depolymerization, which is essential for spindle formation during mitosis. This arrests cells in M phase.

(II) Mitogen treatment: Mitogens like epidermal growth factor stimulate cells to exit G₀ (quiescence) and enter G₁ phase, allowing them to proceed through the cell cycle.

(III) DNA duplication checkpoint: This occurs at the G₂/M checkpoint which verifies that DNA replication is complete before entering mitosis. This corresponds to G₂ phase.

Now matching the graphs to stages:

Graph P: Shows cells with 2C DNA content → G₁ phase
Graph Q: Shows cells with DNA content between 2C-4C → S phase
Graph R: Shows cells with 4C DNA content → G₂ phase
Graph S: Shows cells with decreasing DNA content (4C→2C) → M phase

Matching the activities:

(I) Taxol arrests at M phase → Graph S
(II) Mitogen treatment affects G₁ phase → Graph P
(III) DNA duplication checkpoint at G₂ phase → Graph R

Therefore, the correct matching is: I - S, II - P, III - R

Looking at the options provided:

I - P, II - S, III - Q → Incorrect
I - R, II - Q, III - S → Incorrect
I - P, II - Q, III - R → Incorrect
I - Q, II - S, III - R → Incorrect

Note: None of the given options exactly match our analysis (I-S, II-P, III-R). However, based on the question and standard cell cycle knowledge, this is the correct identification.

Key Formulae

DNA content changes during cell cycle:

G_{1} : 2 C, S : 2 C \to 4 C, G_{2} / M : 4 C, After division : 2 C

Related Topics

Key Formulae