During prophase, the first stage of mitosis, several key events occur to prepare the cell for the division of its genetic material. These events include:
- Chromosome condensation : The chromosomes in the nucleus start to condense, making them easier to pull apart later on during mitosis
- Formation of the mitotic spindle : The cell's two centrosomes move towards opposite poles, and microtubules gradually assemble between them, forming the network that will later pull the duplicated chromosomes apart
- Breakdown of the nuclear membrane : The nuclear membrane breaks down, allowing the spindle microtubules to have direct access to the genetic material of the cell
- Disappearance of the nucleolus : The nucleolus, a part of the nucleus where ribosomes are made, disappears, indicating that the nucleus is getting ready to break down
- Formation of kinetochores : The kinetochores of sister chromatids are oriented on opposite sides of the chromosome, allowing them to attach to microtubules
After the completion of prophase, the cell enters prometaphase, a transition period between prophase and metaphase. During prometaphase, the spindle microtubules attach to the kinetochores of the condensed chromosomes
