Which character marks the beginning of the second phase of mitosis ?

Options

A. Appearance of chromosomes
B. Initiation of spindle
C. Disintegration of nuclear envelope
D. Formation of equatorial plate

Answer

To determine which character marks the beginning of the second phase of mitosis, we first need to understand the stages of mitosis. Mitosis is divided into four main phases:

1. **Prophase**
2. **Metaphase**
3. **Anaphase**
4. **Telophase**

The second phase of mitosis is **Metaphase**. Now, let's analyze the options provided in the question:

1. **Appearance of chromosomes**: This occurs during Prophase when the chromatin condenses to form visible chromosomes.

2. **Initiation of spindle**: The formation of the mitotic spindle also occurs during Prophase, as the spindle fibers begin to form and attach to the chromosomes.

3. **Disintegration of nuclear envelope**: This process occurs during Prophase as well, when the nuclear envelope breaks down to allow the spindle fibers to access the chromosomes.

4. **Formation of equatorial plate**: This is the characteristic that marks the beginning of Metaphase. During this phase, chromosomes align at the metaphase plate (equatorial plane) in preparation for separation.

Based on this analysis, the correct answer to the question is:

**Formation of equatorial plate**.

### Step-by-Step Solution:
1. Identify the phases of mitosis: Prophase, Metaphase, Anaphase, and Telophase.
2. Determine which phase is the second: Metaphase.
3. Analyze the options:
- Appearance of chromosomes: Occurs in Prophase.
- Initiation of spindle: Occurs in Prophase.
- Disintegration of nuclear envelope: Occurs in Prophase.
- Formation of equatorial plate: Marks the beginning of Metaphase.
4. Conclude that the correct answer is the formation of the equatorial plate.