Mitosis Process: Cell Division, Stages and Functions

Mitosis: Process and Purpose

Mitosis is a process of asexual cell division in which a diploid stem cell produces two cells equal to each other and identical to the mother cell. The two daughter cells have the same number of chromosomes as the parent cell and identical genetic information. The only difference is that their chromosomes are single (one chromatid) instead of the double chromosomes from the mother cell.

Function in Organisms

Mitosis in unicellular organisms serves to increase the number of individuals. In multicellular organisms, it serves for individual growth, regeneration of lost cells, and repair of damaged structures. Mitosis is divided into four stages which are not always sharply defined. Distinguish between mitosis (nuclear division) and the division of the cytoplasm, cytokinesis.

Stages of Mitosis

Prophase: It starts with the disappearance of the nucleolus, nuclear membrane, and Golgi apparatus. Chromatin begins to condense and form chromosomes. The centrioles begin to separate and duplicate to make two procentrioles. Each pair is directed to areas of the cell opposite each other, marking the future axis of division; this is especially important in plants as it marks the direction in which future cells will grow.

Metaphase: Metaphase begins with the formation of microtubule filaments located between the centrioles, arranged from pole to pole in a spindle shape. Microtubules attach to chromosomes. Fully formed chromosomes attach to spindle filaments through the centromere. Chromosomes are arranged on the central equatorial plate.

Anaphase: The spindle filaments begin to shorten and separate the sister chromatids at the centromere. They stretch and pull them toward the two ends (poles) of the cell. The ends of the chromatid arms may lag behind the centromere, which moves ahead.

Telophase: The chromosomes begin to reach the polar zones. Spindle filaments disappear and the chromosomes begin to decondense. The nuclear membrane begins to reform. The membrane is finally complete and the chromosomes have been transformed back into chromatin. Nucleoli reappear and then the Golgi apparatus, which concludes the division of the nucleus. Normally the division of the cytoplasm occurs simultaneously.

Cytokinesis in Animals and Plants

In animal cells, at the equator the membrane forms a ring of contractile fibers that compress and constrict the cell, forming a cleavage furrow. In plant cells, materials are deposited between the two sides of the cell and a cell plate is formed, eventually dividing the cell into two.

Key Points

• Mitosis produces two genetically identical daughter cells.
• It plays roles in growth, regeneration, repair, and reproduction (in unicellular organisms).
• Mitosis (nuclear division) is distinct from cytokinesis (cytoplasmic division).
• The classical stages are Prophase, Metaphase, Anaphase, and Telophase.