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As this happens, microtubules invade the nuclear space. This is called open mitosis, and it occurs in some multicellular organisms. Fungi and some protists, such as algae or trichomonads, undergo a variation called closed mitosis where the spindle forms inside the nucleus, or the microtubules penetrate the intact nuclear envelope. [45] [46]
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. During cytokinesis the spindle ...
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.
In general, mitosis (division of the nucleus) is preceded by the S stage of interphase (during which the DNA replication occurs) and is followed by telophase and cytokinesis; which divides the cytoplasm, organelles, and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components.
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.
The cell cycle begins with interphase when the DNA replicates, the cell grows and prepares to enter mitosis. Mitosis includes four phases: prophase , metaphase , anaphase , and telophase . Prophase is the initial phase when spindle fibers appear that function to move the chromosomes toward opposite poles.
Interphase – The stages of the cell cycle that prepare the cell for division. Mitosis – In eukaryotes, the process of division of the nucleus and genetic material. Prophase – The stage of mitosis in which the chromatin condenses into a highly ordered structure called chromosomes and the nuclear membrane begins to break up.
In addition to the breakdown of the nuclear membrane during the prometaphase stage of mitosis, the nuclear membrane also ruptures in migrating mammalian cells during the interphase stage of the cell cycle. [20] This transient rupture is likely caused by nuclear deformation.