Spindles are arrested by colchicine at

Options

A. anaphase
B. metaphase
C. telophase
D. prophase

Answer

To solve the question "Spindles are arrested by colchicine at," we need to understand the role of colchicine in the cell cycle and specifically during mitosis. Here’s a step-by-step breakdown:

### Step 1: Understand Colchicine
Colchicine is an alkaloid that disrupts the formation of spindle fibers by inhibiting their polymerization. This means that it prevents the spindle fibers from forming properly, which is crucial for the separation of chromosomes during cell division.

**Hint:** Remember that colchicine affects the spindle fibers, which are essential for chromosome movement during mitosis.

### Step 2: Review the Stages of Mitosis
Mitosis consists of several stages:
- **Prophase:** Chromosomes condense and become visible; the nuclear envelope begins to break down.
- **Metaphase:** Chromosomes align at the metaphase plate in the center of the cell.
- **Anaphase:** Sister chromatids are pulled apart towards opposite poles of the cell.
- **Telophase:** Chromosomes decondense, and the nuclear envelope re-forms around each set of chromosomes.

**Hint:** Familiarize yourself with the key events that occur in each stage of mitosis.

### Step 3: Identify the Effect of Colchicine
Since colchicine prevents the polymerization of spindle fibers, it effectively halts the process of chromosome separation. This means that if the spindle fibers are not functioning properly, the cell cannot proceed from metaphase to anaphase.

**Hint:** Consider which stage would be directly impacted by the inability to form functional spindle fibers.

### Step 4: Determine the Correct Stage
Given that colchicine arrests the spindle fibers, the cell will be unable to transition from metaphase (where chromosomes are aligned at the center) to anaphase (where they are separated). Therefore, colchicine effectively arrests the cell cycle at the metaphase stage.

**Hint:** Think about the alignment of chromosomes and how spindle fibers are crucial for their separation.

### Conclusion
The correct answer to the question "Spindles are arrested by colchicine at" is **Metaphase**.

### Final Answer
**Option B: Metaphase**