During the formation of the spindle apparatus in mitosis, which of the following structures must break down?

• A. Mitochondrial membrane
• B. Nuclear envelope
• C. Cell membrane
• D. Golgi apparatus

Answer: (B)

Verified step by step guidance

1. Understand the context of mitosis: Mitosis is a process of cell division that results in two genetically identical daughter cells from a single parent cell. It involves several stages, including prophase, metaphase, anaphase, and telophase.
2. Identify the role of the nuclear envelope: The nuclear envelope is a double membrane structure that encloses the nucleus, separating it from the cytoplasm. It plays a crucial role in protecting the genetic material during interphase.
3. Recognize the changes during prophase: During prophase, the first stage of mitosis, the chromatin condenses into visible chromosomes, and the spindle apparatus begins to form. For the spindle fibers to access the chromosomes, the nuclear envelope must disassemble.
4. Consider the function of the spindle apparatus: The spindle apparatus is responsible for separating the sister chromatids and ensuring they are evenly distributed to the daughter cells. It requires access to the chromosomes, which is facilitated by the breakdown of the nuclear envelope.
5. Conclude which structure breaks down: Given the need for the spindle apparatus to interact with the chromosomes, the nuclear envelope must break down during prophase to allow this interaction, making it the correct answer.