The complete disintegration of nuclear envelope marks the:

Options

A. Early prophase
B. start of second phase of mitosis
C. End of first phase of mitosis
D. End of second phase of mitosis

Answer

To answer the question regarding the complete disintegration of the nuclear envelope, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Cell Cycle**: The cell cycle consists of several phases, including interphase and the M phase (mitotic phase). The M phase is where cell division occurs.

2. **Identifying the M Phase Stages**: The M phase is divided into four main stages: Prophase, Metaphase, Anaphase, and Telophase.

3. **Focusing on Prophase**: During Prophase, the chromatin condenses into chromosomes, and the nuclear envelope begins to break down. This is the first stage of the M phase.

4. **Disintegration of Nuclear Envelope**: The complete disintegration of the nuclear envelope occurs towards the end of Prophase. This is a crucial step that allows the spindle fibers to access the chromosomes.

5. **Conclusion**: Therefore, the complete disintegration of the nuclear envelope marks the end of Prophase in the M phase of the cell cycle.

### Final Answer:
The complete disintegration of the nuclear envelope marks the end of Prophase.

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