Here's why:
* Prophase: The nuclear membrane starts to break down, but it's not completely gone yet. You can still see fragments of it as the chromosomes condense and become more visible.
* Metaphase: The nuclear membrane has completely disappeared, allowing the chromosomes to line up at the equator of the cell.
* Anaphase: The sister chromatids separate and move to opposite poles of the cell. The nuclear membrane remains absent.
* Telophase: The nuclear membrane reforms around the chromosomes at each pole, forming two distinct nuclei.
So, the nuclear membrane is still visible during the early stages of mitosis, particularly prophase.
