1. Interphase:
* This is the "preparation" phase before mitosis begins. The cell grows, duplicates its DNA (chromosomes), and produces the necessary organelles for the new cells.
* It's not technically part of mitosis, but it's essential for the process to occur correctly.
2. Prophase:
* Chromosomes condense and become visible.
* The nuclear envelope (membrane surrounding the nucleus) breaks down.
* The spindle fibers, made of microtubules, begin to form from the centrosomes.
* Centrosomes migrate to opposite poles of the cell.
3. Metaphase:
* The chromosomes line up along the equator of the cell, forming the metaphase plate.
* The spindle fibers attach to the centromeres (the region where two sister chromatids are joined) of each chromosome.
4. Anaphase:
* The sister chromatids of each chromosome are pulled apart by the spindle fibers.
* The two sets of chromosomes move to opposite poles of the cell.
5. Telophase:
* The chromosomes reach the poles of the cell and begin to uncoil and become less visible.
* The nuclear envelope reforms around each set of chromosomes.
* The cytoplasm divides (cytokinesis), forming two separate daughter cells.
Cytokinesis:
* This is the physical division of the cytoplasm, which occurs alongside telophase.
* In animal cells, a cleavage furrow forms and pinches inward, dividing the cytoplasm.
* In plant cells, a cell plate forms between the two daughter cells, eventually becoming a new cell wall.
Key points:
* Mitosis ensures that each daughter cell receives an identical copy of the parent cell's DNA.
* The process is tightly regulated by a complex network of proteins that control the progression through each stage.
* Errors in mitosis can lead to abnormal cell division and potentially cancer.
By understanding the steps of mitosis, we can better comprehend how organisms grow, repair tissues, and maintain their genetic integrity.
