During which phase of mitosis do chromosomes become visible, spindle fibers form, and the nucleus disappears?

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

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the phases of mitosis. Mitosis is divided into several phases: prophase, metaphase, anaphase, and telophase. Each phase has distinct characteristics and events.
2. Step 2: Recall the events of prophase. During prophase, chromosomes condense and become visible under a microscope. Spindle fibers begin to form, and the nuclear envelope starts to break down, causing the nucleus to disappear.
3. Step 3: Compare the events of prophase with the other phases. In metaphase, chromosomes align at the cell's equatorial plate. In anaphase, sister chromatids are pulled apart to opposite poles. In telophase, the nuclear envelope reforms, and chromosomes decondense.
4. Step 4: Match the description in the problem to the correct phase. The problem mentions visible chromosomes, spindle fiber formation, and the disappearance of the nucleus, which are all characteristics of prophase.
5. Step 5: Conclude that the correct answer is prophase based on the alignment of the described events with the characteristics of this phase.