All of the following occur during prophase of mitosis except:

• A. Sister chromatids separate and move to opposite poles
• B. The nuclear envelope begins to break down
• C. Spindle fibers begin to form
• D. Chromatin condenses into visible chromosomes

Answer: (A)

Verified step by step guidance

1. Review the key events that occur during prophase of mitosis, focusing on the structural changes within the cell.
2. Recall that during prophase, chromatin condenses into visible chromosomes, making them easier to separate later.
3. Understand that the nuclear envelope begins to break down in prophase to allow spindle fibers access to chromosomes.
4. Recognize that spindle fibers start to form during prophase to eventually attach to chromosomes for segregation.
5. Note that sister chromatids do not separate and move to opposite poles during prophase; this event occurs later during anaphase.