What is Mitosis? mitosis definition is the division of the mother cell into two daughter cells genetically identical to each other.
It is a nuclear division plus cytokinesis and produces two identical daughter cells during prophase, prometaphase, metaphase, anaphase, and telophase. Interphase is often included in discussions of mitosis, but interphase is technically not part of the mitotic process, but rather encompasses stages G1, S, and G2 of the cell cycle.
Mitosis Stages: Interphase & mitosis
The cell is engaged in a metabolic activity and performing its prepare for mitosis (the next four phases that lead up to and include nuclear division). Chromosomes are not clearly discerned in the nucleus, although a dark spot called the nucleolus may be visible. The cell may contain a pair of centrioles (or microtubule organizing centers in plants) both of which are organizational sites for microtubules.
In Mitosis Prophase, Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres. Some fibers cross the cell to form the mitotic spindle.
The nuclear membrane dissolves, marking the beginning of prometaphase. Proteins attach to the centromeres creating the kinetochores. Microtubules attach at the kinetochores and the chromosomes begin moving.
Spindle fibers align the chromosomes along the middle of the cell nucleus. This line is referred to as the metaphase plate. This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome.
The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Motion results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules.
Chromatids arrive at opposite poles of the cell, and new membranes form around the daughter nuclei. The chromosomes disperse and are no longer visible under the light microscope. The spindle fibers disperse, and cytokinesis or the partitioning of the cell may also begin during this stage.
Telophase & Cytokinesis:
In animal cells, cytokinesis results when a fiber ring composed of a protein called actin around the center of the cell contracts pinching the cell into two daughter cells, each with one nucleus. In plant cells, the rigid wall requires that a cell plate is synthesized between the two daughter cells.
Why is Mitosis important?
- Mitosis is important because some organisms do not sexually reproduce.
- Bacteria is a great example of this.
- Without mitosis, we would not have many of these types of organisms.
- Another importance is Growth. The number of cells within an organism increases by this process and this is the basis of growth in multicellular organisms.
- Cell Replacement. Cells are constantly sloughed off, dying and being replaced by new ones in the skin and digestive tract.
- When damaged tissues are repaired, the new cells must be exact copies of the cells being replaced so as to retain the normal function of cells.
- Regeneration. Some animals can regenerate parts of the body, and production of new cells are achieved by the mitotic process.
- Vegetative Reproduction. Some plants produce offspring which are genetically similar to themselves. These offspring are called clones.