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The Editors of Encyclopaedia Britannica Last Updated: Jul 29, 2024 • Article History Table of Contents
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Top Questions What is mitosis?Mitosis is a process of cell duplication, in which one cell divides into two genetically identical daughter cells. In the various stages of mitosis, the cell’s chromosomes are copied and then distributed equally between the two new nuclei of the daughter cells.
How are mitosis and meiosis different?Mitosis is the division of a cell into two daughter cells that are genetically identical to the parent cell. Meiosis is the division of a germ cell into four sex cells (e.g. egg or sperm), each with half the number of chromosomes of the parent cell. Mitosis is a means of asexual reproduction, whereas meiosis is necessary for sexual reproduction.
Why is mitosis important to organisms?Mitosis is important to multicellular organisms because it provides new cells for growth and for replacement of worn-out cells, such as skin cells. Many single-celled organisms rely on mitosis as their primary means of asexual reproduction.
mitosis, a process of cell duplication, or reproduction, during which one cell gives rise to two genetically identical daughter cells. Strictly applied, the term mitosis is used to describe the duplication and distribution of chromosomes, the structures that carry the genetic information.
Prior to the onset of mitosis, the chromosomes have replicated and the proteins that will form the mitotic spindle have been synthesized. Mitosis begins at prophase with the thickening and coiling of the chromosomes. The nucleolus, a rounded structure, shrinks and disappears. The end of prophase is marked by the beginning of the organization of a group of fibres to form a spindle and the disintegration of the nuclear membrane.
The chromosomes, each of which is a double structure consisting of duplicate chromatids, line up along the midline of the cell at metaphase. In anaphase each chromatid pair separates into two identical chromosomes that are pulled to opposite ends of the cell by the spindle fibres. During telophase, the chromosomes begin to decondense, the spindle breaks down, and the nuclear membranes and nucleoli re-form. The cytoplasm of the mother cell divides to form two daughter cells, each containing the same number and kind of chromosomes as the mother cell. The stage, or phase, after the completion of mitosis is called interphase.
Mitosis is absolutely essential to life because it provides new cells for growth and for replacement of worn-out cells. Mitosis may take minutes or hours, depending upon the kind of cells and species of organisms. It is influenced by time of day, temperature, and chemicals.
The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Meg Matthias.
