During which phase of mitosis does the nuclear membrane break down?

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

Answer: (D)

Verified step by step guidance

1. Understand the stages of mitosis: Mitosis is divided into several phases: prophase, metaphase, anaphase, and telophase. Each phase has distinct events that occur within the cell.
2. Identify the key events in prophase: During prophase, the chromatin condenses into visible chromosomes, and the mitotic spindle begins to form. Importantly, the nuclear membrane starts to break down, allowing the spindle fibers to interact with the chromosomes.
3. Compare prophase with other phases: In metaphase, chromosomes align at the cell's equatorial plane. In anaphase, sister chromatids are pulled apart to opposite poles. In telophase, the nuclear membrane reforms around the separated sets of chromosomes.
4. Recognize the significance of nuclear membrane breakdown: The breakdown of the nuclear membrane is crucial for the spindle fibers to access and attach to the chromosomes, facilitating their movement during mitosis.
5. Conclude that the nuclear membrane breakdown occurs in prophase: Based on the events described, the nuclear membrane breaks down during prophase, setting the stage for chromosome alignment and separation in subsequent phases.