Mitosis: Understanding the Cell Division Process

Mitosis

Mitosis is a type of cell division that occurs in diploid cells, where chromosomes are separated during cell division so that each daughter cell receives one set of chromosomes. This process allows for growth, healing after injury, and tissue repair through the production of new cells. There are five stages in mitosis: prophase, metaphase, anaphase, telophase, and cytokinesis. In this article, we will explore how these stages work together to create identical copies of cells during mitosis.

Prophase

During prophase, the chromatin condenses into discrete chromosomes as they attach to the nuclear envelope. Nucleoli disappear, spindle fibers form from microtubules, and a centrosome duplicates itself. At the end of the stage, the nuclear membrane breaks down, allowing the DNA to become visible within the nucleus.

Metaphase

In metaphase, spindle fibers attach to the kinetochores on the centromeres of the sister chromatids, aligning them along the mitotic spindle. The microtubules pull evenly in both directions to ensure that the chromosomes are aligned at the center of the dividing cell. At the same time, the protein called cyclin B starts breaking down, which leads to a decrease in Cdk1 activity, stopping further progression through prophase.

Anaphase

At the beginning of anaphase, sister chromatids separate from their kinetochores and move towards opposite ends of the cell due to the tension created by the spindle fibers pulling apart. Each chromosome is now pulled by its respective spindle fiber, leading to the separation of sister chromatids. The protein separase cuts the cohesins between the chromatids, ensuring that they remain separated throughout the remainder of mitosis.

Telophase

During telophase, the sister chromatids reach the opposite poles of the cell and begin to decondense back into chromatin. New nuclear envelopes form around the separated chromatids, and chromosomal proteins reassemble akinetochore fibers at the newly formed kinetochores of the separated chromatids.

Cytokinesis

The final stage of mitosis is cytokinesis. During this stage, the cytoplasm divides, creating two distinct cells. A cleavage furrow forms, eventually splitting the cell in half, and the two new cells emerge from the original cell. After cytokinesis, the resulting cells have exactly the same number of chromosomes as the parental cell.

By understanding these stages and the mechanisms involved in mitosis, we can appreciate how our bodies grow, heal injuries, and maintain homeostasis through the constant production and replacement of cells.