Question at position 7 The nuclear envelope must degenerate (break down) prior to cell division.FalseTrue单项选择题
A
False
B
True

Question

Question at position 7 The nuclear envelope must degenerate (break down) prior to cell division.FalseTrue

BlackTom AI · Accepted Answer

During mitosis in typical eukaryotic cells, the nuclear envelope disassembles so the mitotic spindle can access condensed chromosomes and segregate them to daughter cells.

Relevant knowledge points and concepts:
- Mitosis stages: prophase, prometaphase, metaphase, anaphase, telophase.
- Nuclear envelope structure: double membrane enclosing chromatin and nuclear pores.
- Spindle formation and microtubule–chromosome interactions require direct access to kinetochores on condensed chromosomes.
- Two modes of mitosis: “open” mitosis (nuclear envelope breaks down) and “closed” mitosis (nuclear envelope remains intact in some fungi/yeast).

Step-by-step reasoning:
1. In prophase chromosomes condense and centrosomes begin forming the spindle.
2. At prometaphase the nuclear envelope breaks down (nuclear membrane fragments and nuclear pore complexes disassemble).
3. Breakdown allows spindle microtubules to penetrate the former nuclear space and attach to kinetochores.
4. With attachments established, chromosomes align at the metaphase plate and are pulled apart in anaphase.
5. In telophase the nuclear envelope re-forms around separated chromosome sets, producing two nuclei.

Why the correct answer is correct:
- For the majority of eukaryotic cells studied in standard cell biology (animal and plant cells), nuclear envelope breakdown is a required step so spindle microtubules can capture kinetochores. Without envelope disassembly, the spindle could not properly interact with chromosomes in these cells, preventing accurate segregation.

Why the other option (False) is incorrect:
- “False” would imply the nuclear envelope does not need to break down. That ignores the common mechanism of open mitosis. Although closed mitosis exists (an important exception in some fungi and protists), the general and expected statement in introductory biology is that the nuclear envelope must break down prior to division.

Conclusion:
The correct choice is True, which matches the provided answer.

Question at position 7 The nuclear envelope must degenerate (break down) prior to cell division.FalseTrue单项选择题

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