Question

During mitosis ER and nucleolus begin to disappear at

• A. late prophase
• B. early metaphase
• C. late metaphase
• D. early prophase

Answer 1

Answer:

D. early prophase

• During mitosis, the endoplasmic reticulum (ER) and nucleolus disappear at early prophase.

• During early prophase, the chromatin condenses, and the nuclear envelope breaks down.

• As the nuclear envelope breaks down, the ER, which is continuous with the nuclear membrane, also starts to disassemble—the disassembly of the ER results in its disappearance from the cytoplasm during early prophase.

• Similarly, during early prophase, the nucleolus, which is responsible for ribosome assembly, also starts to disappear.

• As the chromatin condenses and the nuclear envelope breaks down, the nucleolus undergoes reorganization and disperses within the nucleus.