Mitosis is the process of cell division in which a single cell divides into two identical daughter cells. It consists of several distinct stages, each with specific events and processes. Here are the stages of mitosis:
- Interphase: This is not technically a stage of mitosis but an important preparatory phase. During interphase, the cell grows, carries out its normal functions, replicates its DNA, and prepares for division. Interphase can be further divided into three subphases: G1 (gap phase 1), S (synthesis phase), and G2 (gap phase 2).
- Prophase: The first stage of mitosis is prophase. In this stage, the chromatin, which consists of long, thin strands of DNA, condenses and becomes visible as distinct chromosomes. The nuclear membrane begins to dissolve, and the centrosomes move to opposite poles of the cell, organizing the spindle apparatus.
- Prometaphase: During prometaphase, the nuclear membrane completely breaks down, and the spindle fibers attach to the kinetochores, which are protein structures on the centromeres of the chromosomes. The chromosomes become highly condensed and align at the center of the cell.
- Metaphase: In metaphase, the chromosomes line up along the equatorial plane, forming a single row called the metaphase plate. The spindle fibers attached to the kinetochores of each chromosome pull them towards opposite poles of the cell.
- Anaphase: Anaphase is characterized by the separation of sister chromatids. The spindle fibers shorten and pull the sister chromatids apart, moving them towards the opposite poles of the cell. This ensures that each daughter cell will receive an identical set of chromosomes.
- Telophase: Telophase marks the final stage of mitosis. The separated chromatids arrive at opposite poles of the cell and begin to decondense. Nuclear envelopes form around each set of chromosomes, creating two distinct nuclei. The spindle apparatus disassembles, and the cell prepares for division.
- Cytokinesis: Cytokinesis, which overlaps with the latter part of telophase, is the physical separation of the cytoplasm and organelles to form two daughter cells. In animal cells, a contractile ring of actin filaments forms a cleavage furrow, pinching the cell in two. In plant cells, a cell plate forms at the equator, gradually developing into a new cell wall to separate the daughter cells.
Once cytokinesis is complete, the cell enters interphase again, and each daughter cell proceeds to carry out its functions, grow, and potentially undergo further rounds of cell division.
Mitosis ensures the accurate distribution of genetic material to daughter cells and is essential for growth, development, tissue repair, and asexual reproduction in multicellular organisms.