lnterzonal fibres appear in

Options

A. anaphase
B. prophase
C. late metaphase
D. early metaphase

Answer

To determine when interzonal fibers (also known as spindle fibers) appear during the cell cycle, we can analyze the different phases of mitosis:

1. **Understanding the Phases of Mitosis**:
- Mitosis is divided into several phases: prophase, metaphase, anaphase, and telophase.
- Each phase has distinct characteristics and processes.

2. **Prophase**:
- During prophase, the chromatin condenses into visible chromosomes, and the nuclear envelope begins to break down.
- The spindle apparatus starts to form, but the interzonal fibers are not fully established yet.

3. **Metaphase**:
- Metaphase is characterized by the alignment of chromosomes along the metaphase plate.
- There are two sub-phases: early metaphase and late metaphase.
- In early metaphase, the spindle fibers attach to the kinetochores of the chromosomes.

4. **Late Metaphase**:
- In late metaphase, the spindle fibers (interzonal fibers) are fully formed and are crucial for the proper alignment and separation of chromosomes.
- This is the phase where the interzonal fibers become prominent and play a key role in preparing for the next phase.

5. **Anaphase**:
- During anaphase, the spindle fibers pull the sister chromatids apart towards opposite poles of the cell.
- While interzonal fibers are present, they were already established during late metaphase.

6. **Conclusion**:
- The appearance of interzonal fibers occurs primarily during late metaphase, making it the correct answer to the question.

**Final Answer**: Interzonal fibers appear in late metaphase.

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