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How does mitosis work?

Published in Cell Division 2 mins read

Mitosis is the process where a single cell divides into two identical daughter cells, a fundamental process for growth, repair, and asexual reproduction. During mitosis, a cell duplicates all of its contents, including its chromosomes, and splits to form two identical daughter cells. Because this process is so critical, the steps of mitosis are carefully controlled by certain genes. When mitosis is not regulated correctly, health problems such as cancer can result.

Here's a breakdown of how mitosis works:

The Stages of Mitosis

Mitosis is generally divided into distinct phases for easy understanding, though it's a continuous process.

  • Prophase: Chromosomes condense and become visible. The nuclear envelope breaks down, and the mitotic spindle (made of microtubules) begins to form.
  • Prometaphase: The nuclear envelope completely disappears. Microtubules of the spindle attach to the chromosomes at the centromere via a structure called the kinetochore.
  • Metaphase: The chromosomes line up along the middle of the cell, at the "metaphase plate".
  • Anaphase: The sister chromatids (identical copies of each chromosome) separate and are pulled towards opposite poles of the cell by the shortening microtubules.
  • Telophase: The chromosomes arrive at the poles and begin to decondense. The nuclear envelope reforms around each set of chromosomes, and the mitotic spindle breaks down.

Cytokinesis: The Final Step

While often discussed alongside mitosis, cytokinesis is technically a separate process. It’s the division of the cytoplasm to fully separate the two newly formed daughter cells. In animal cells, this involves the formation of a cleavage furrow, which pinches the cell in two. In plant cells, a cell plate forms in the middle of the cell, eventually becoming a new cell wall.

Regulation of Mitosis

The process of mitosis is tightly regulated by various genes and proteins to ensure accuracy. Cell cycle checkpoints monitor for errors and halt the process if something goes wrong. When mitosis is not regulated correctly, health problems such as cancer can result. (Reference)

Why Mitosis is Important

  • Growth: Mitosis allows organisms to increase in size by adding more cells.
  • Repair: It replaces damaged or worn-out cells.
  • Asexual Reproduction: In some organisms, mitosis is the primary mode of reproduction.

Problems with Mitosis

Problems in mitosis, like incorrect chromosome segregation, can lead to:

  • Aneuploidy: An abnormal number of chromosomes in a cell.
  • Cancer: Uncontrolled cell division caused by a failure in the regulation of mitosis.