In which phase of mitosis spindle fibres attach to kinetochores of chromosomes.

Options

A. Prophase
B. Metaphase
C. Anaphase
D. Telophase

Answer

To determine in which phase of mitosis spindle fibers attach to the kinetochores of chromosomes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Mitosis Phases**: Mitosis consists of several phases: prophase, metaphase, anaphase, and telophase. Each phase has distinct characteristics and events.

2. **Identifying Prophase**: In prophase, the chromatin condenses into visible chromosomes, and the nuclear envelope begins to break down. However, spindle fibers have not yet attached to the kinetochores at this stage.

3. **Identifying Metaphase**: During metaphase, chromosomes align at the metaphase plate (the equatorial plane of the cell). This is the critical phase where spindle fibers attach to the kinetochores of the chromosomes. The kinetochores are protein structures on the chromosome that serve as attachment points for the spindle fibers.

4. **Identifying Anaphase**: In anaphase, the spindle fibers pull the sister chromatids apart toward opposite poles of the cell. While the spindle fibers are still present, they are no longer attaching to the kinetochores; instead, they are pulling the chromatids apart.

5. **Identifying Telophase**: In telophase, the chromosomes reach the poles and begin to de-condense back into chromatin. The nuclear envelope re-forms around each set of chromosomes, and the spindle fibers disassemble. There is no attachment to kinetochores in this phase.

6. **Conclusion**: Based on the analysis, the phase of mitosis where spindle fibers attach to kinetochores of chromosomes is **metaphase**.

### Final Answer:
The spindle fibers attach to the kinetochores of chromosomes during **metaphase**.

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