At metaphase, chromosmes are attached to the spindle fibres by their

Options

A. Centrosome
B. Chromomere
C. Chromonema
D. Kinetochore

Answer

**Step-by-Step Solution:**

1. **Understanding Metaphase**: Metaphase is a stage in cell division where chromosomes align at the cell's equatorial plane. During this phase, it is crucial for chromosomes to be properly attached to the spindle apparatus to ensure accurate separation.

2. **Role of Spindle Fibers**: Spindle fibers are thread-like structures composed of microtubules. They originate from the centrosomes and play a vital role in the movement of chromosomes during cell division.

3. **Attachment of Chromosomes**: During metaphase, each chromosome is attached to spindle fibers at a specific region. This region is crucial for the proper alignment and separation of chromosomes.

4. **Identifying the Correct Structure**: The question asks what structure the chromosomes are attached to during metaphase. The options provided include centrosome, centromere, chromonema, and kinetochore.

5. **Analyzing the Options**:
- **Centrosome**: This is involved in the formation of spindle fibers but is not where chromosomes attach.
- **Centromere**: This is the region where two sister chromatids are joined, but it does not directly attach to spindle fibers.
- **Chromonema**: This refers to the coiled structure of chromosomes but is not involved in the attachment to spindle fibers.
- **Kinetochore**: This is the correct structure. The kinetochore is a protein complex that forms at the centromere and serves as the attachment point for spindle fibers.

6. **Conclusion**: Therefore, the correct answer to the question is that at metaphase, chromosomes are attached to the spindle fibers by their **kinetochores**.

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