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In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre [1]) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle progression. The centrosome provides structure for the cell.
Centrosome disorientation refers to the loss of orthogonality between the mother and daughter centrioles. [2] Once disorientation occurs, the mature centriole begins to move toward the cleave furrow. It has been proposed that this movement is a key step in abscission , the terminal phase of cell division.
In this diagram of a duplicated chromosome, (2) identifies the centromere—the region that joins the two sister chromatids, or each half of the chromosome.In prophase of mitosis, specialized regions on centromeres called kinetochores attach chromosomes to spindle fibers.
γ-tubulin is a protein located at the centrosome that nucleates the microtubules by interacting with the tubulin monomer subunit in the microtubule at the minus end. [1] Organization of the microtubules at the MTOC, or centrosome in this case, is determined by the polarity of the microtubules defined by y-tubulin. [1]
Before the cell enters G1 phase, i.e. before the formation of the cilium, the mother centriole serves as a component of the centrosome. In cells that are destined to have only one primary cilium, the mother centriole differentiates into the basal body upon entry into G1 or quiescence. Thus, the basal body in such a cell is derived from the ...
In the centrosome-mediated "search and capture" model (left), microtubules nucleated from centrosomes contact chromosomes by chance and become stabilized at kinetochores to form the spindle. In the chromatin-mediated "self-organization" model (right), microtubules are nucleated around the vicinity of mitotic chromatin and organized into a ...
Steps of the cell cycle. The restriction point occurs between the G 1 and S phases of interphase.. The restriction point (R), also known as the Start or G 1 /S checkpoint, is a cell cycle checkpoint in the G 1 phase of the animal cell cycle at which the cell becomes "committed" to the cell cycle, and after which extracellular signals are no longer required to stimulate proliferation. [1]
An aster is a cellular structure shaped like a star, consisting of a centrosome and its associated microtubules during the early stages of mitosis in an animal cell. [1]: 221 Asters do not form during mitosis in plants. Astral rays, composed of microtubules, radiate from the centrosphere and look like a cloud. Astral rays are one variant of ...