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The mitosis process in the cells of eukaryotic organisms follows a similar pattern, but with variations in three main details. "Closed" and "open" mitosis can be distinguished on the basis of nuclear envelope remaining intact or breaking down. An intermediate form with partial degradation of the nuclear envelope is called "semiopen" mitosis.
Mitotic cell division enables sexually reproducing organisms to develop from the one-celled zygote, which itself is produced by fusion of two gametes, each having been produced by meiotic cell division. [5] [6] After growth from the zygote to the adult, cell division by mitosis allows for continual construction and repair of the organism. [7]
As mitosis starts, the nuclear envelope disintegrates, chromosomes condense and become visible, and the cell prepares for division. Cyclin B-Cdk1 activation results in nuclear envelope breakdown, which is a characteristic of the initiation of mitosis. [1]
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
The main components of the nuclear envelope are a double membrane, nuclear pore complexes, and a nuclear lamina internal to the inner nuclear membrane. These components are dismantled during prophase and prometaphase and reconstructed during telophase, when the nuclear envelope reforms on the surface of separated sister chromatids.
Cytokinesis (/ ˌ s aɪ t oʊ k ɪ ˈ n iː s ɪ s /) is the part of the cell division process and part of mitosis during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division in mitosis and meiosis.
Interkinetic nuclear migration is a feature of developing neuroepithelia and is characterized by the periodic movement of the cell’s nucleus with the progression of the cell cycle. Developing neuroepithelia are tissues composed of neural progenitor cells, each spanning the entire thickness of the epithelium from the ventricular surface to the ...
Mitosis divides the chromosomes in a cell nucleus. During mitosis chromosome segregation occurs routinely as a step in cell division (see mitosis diagram). As indicated in the mitosis diagram, mitosis is preceded by a round of DNA replication, so that each chromosome forms two copies called chromatids.