Question

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the animal cell cycle would be most disrupted by cytochalasin B?

(A) Spindle formation

(B) Spindle attachment to kinetochores

(C) Cell elongation during anaphase

(D) Cleavage furrow formation and cytokinesis

Short answer

(A) The option “Spindle formation” is false.

(B) The option “Spindle attachment to kinetochores” is false.

(C) The option “Cell elongation during anaphase” is false.

(D) The option “Cleavage furrow formation and cytokinesis” is true.

Step-by-step solution

Description of cell cycle

The series of steps that help the cell to grow and divide is known as the cell cycle. There are few checkpoints in between each stage of the cell cycle to regulate the proper synthesis of cells.

Explanation of option (A)

There is a specific type of drug that blocks the formation of spindle fibers. It hinders microtubule polymerization.

Spindle fiber formation does not happen in the cytokinesis stage, so the drug does not block this step.

Therefore, the given statement is false.

Explanation of option (B)

After the formation of spindle fibers, these fibers get attached to the kinetochore of the chromosome. It is a protein structure present in the chromosomes.

Cytochalasin does not interrupt the attachment of the spindle with the kinetochore. It is specific to actin polymerization.

Therefore, the given statement is false.

Explanation of option (C)

Cytochalasin does not interrupt the anaphase. It acts only on the contractile filaments’ formation.

Anaphase is associated with the cytokinesis step, so the drug does not hinder this step.

Therefore, the given statement is false.

Explanation of option (D)

Cleavage furrow formation is the beginning of the cytokinesis process. In this phase, the daughter cells are formed completely. Cytochalasin B binds with the actin and hinders the process of polymerization of actin.

The cytochalasin B hinders the cytoplasmic division of the cell alone in the case of animal cells. It does not impede the nuclear division mechanism of the cell.

Therefore, the given statement is true.