Prophase

Definition

Prophase is the first stage of mitosis, where chromatin condenses into visible chromosomes. The nuclear envelope begins to disintegrate and spindle fibers start to form from the centrosomes.

5 Must Know Facts For Your Next Test

1. During prophase, each chromosome consists of two sister chromatids joined at the centromere.
2. The nucleolus disappears as the chromatin condenses into chromosomes.
3. Spindle fibers emerge from the centrosomes, which begin to move toward opposite poles of the cell.
4. The breakdown of the nuclear envelope marks a key event in prophase.
5. Prophase sets the stage for metaphase by preparing chromosomes for alignment along the metaphase plate.

Review Questions

• What happens to chromatin during prophase?
• Why is the disintegration of the nuclear envelope significant in prophase?
• How do spindle fibers contribute to cell division during prophase?

Related terms

Metaphase: In metaphase, chromosomes align along the metaphase plate, equidistant from both spindle poles.

Anaphase: Anaphase is characterized by sister chromatids separating and moving toward opposite poles of the cell.

Telophase: Telophase involves reformation of the nuclear envelope around separated chromosomes, which decondense back into chromatin.