The stage of mitosis that takes the longest to complete is prophase. This is primarily determined by the extensive processes that occur during this phase, which set the stage for the subsequent steps of mitosis.
During prophase, several key events take place:
- Chromatin condensation: The chromatin fibers condense into distinct chromosomes, making them easier to separate later on.
- Formation of the mitotic spindle: The mitotic spindle begins to form, originating from structures called centrosomes. These spindles play a critical role in moving the chromosomes during cell division.
- Nuclear envelope disintegration: The nuclear envelope starts breaking down, allowing the spindle fibers to access the chromosomes.
Prophase is a complex process that requires significant cellular reorganization, which contributes to its lengthy duration compared to other stages of mitosis.