Mitosis is divided into four main stages that allow a cell to divide its copied DNA evenly into two identical daughter cells. These stages are prophase, metaphase, anaphase, and telophase, often followed by cytokinesis to complete cell division.
Steps
During prophase, the chromatin condenses into visible chromosomes, each consisting of two sister chromatids joined at the centromere. The nuclear envelope breaks down and spindle fibers begin to form from the centrosomes.
In metaphase, the chromosomes line up along the center of the cell at the metaphase plate. Spindle fibers attach to the centromere of each chromosome, ensuring each sister chromatid is connected to opposite poles of the cell.
During anaphase, the sister chromatids separate and are pulled apart by the spindle fibers toward opposite ends of the cell. This ensures each new cell will receive an identical set of chromosomes.
In telophase, the chromosomes begin to uncoil back into chromatin, and a new nuclear envelope forms around each set of chromosomes. The spindle fibers disappear, creating two distinct nuclei within one cell.
Cytokinesis usually overlaps with telophase and completes the division process. The cytoplasm divides, and in animal cells, a cleavage furrow pinches the cell into two separate daughter cells.
Worked example
Imagine a skin cell with 46 chromosomes undergoing mitosis. During prophase, those 46 chromosomes become visible. In metaphase, they align in the middle. During anaphase, the sister chromatids split, so 46 chromatids move to each side. By telophase, each side has 46 chromosomes forming a new nucleus. After cytokinesis, you have two skin cells, each with 46 chromosomes, identical to the original.
Remember
Mitosis consists of prophase, metaphase, anaphase, and telophase, working together to create two genetically identical daughter cells from one parent cell.