What are the major features of prophase in mitosis?

Options

A. Chromosome condense
B. Crossing-over between homologous chromosomes
C. Nuclear envelope breaks up
D. Chiasmata formation

Explanation

### Step-by-Step Solution:

1. **Chromosome Condensation**:
- During prophase, the chromatin fibers condense into distinct chromosomes. Each chromosome becomes more compact, making them visible under a microscope. This condensation is crucial for the chromosomes to be accurately separated later in mitosis.

2. **Disintegration of the Nuclear Envelope**:
- The nuclear envelope, which surrounds the nucleus, begins to break down and disintegrate. This process allows the chromosomes to move freely in the cytoplasm and is essential for the subsequent stages of mitosis.

3. **Appearance of Centrosomes**:
- Centrosomes, which are organelles that play a key role in cell division, start to appear and move towards opposite poles of the cell. They are responsible for organizing the spindle fibers that will help separate the chromosomes during mitosis.

4. **Formation of Spindle Fibers**:
- As the centrosomes move apart, they begin to form spindle fibers. These fibers extend from the centrosomes and attach to the chromosomes at their centromeres, preparing for the alignment and separation of chromosomes in the next phase of mitosis.

5. **Visual Observation**:
- Under a microscope, prophase is characterized by the visibility of condensed chromosomes and the absence of the nuclear envelope. The distinct X-shaped structures of chromosomes can be clearly observed, indicating that the cell is ready to proceed to the next phase of mitosis.