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It is referred to as the mitotic spindle during mitosis, a process that produces genetically identical daughter cells, or the meiotic spindle during meiosis, a process that produces gametes with half the number of chromosomes of the parent cell. Besides chromosomes, the spindle apparatus is composed of hundreds of proteins.
The spindle checkpoint, also known as the metaphase-to-anaphase transition, the spindle assembly checkpoint (SAC), the metaphase checkpoint, or the mitotic checkpoint, is a cell cycle checkpoint during metaphase of mitosis or meiosis that prevents the separation of the duplicated chromosomes until each chromosome is properly attached to the ...
The mitotic spindle checkpoint verifies that all the chromosomes are aligned properly on the metaphase plate and prevents premature entry into anaphase. Chromosomes lined up on the metaphase plate. Two views with the metaphase plate rotated 60°. Stages of early mitosis in a vertebrate cell with micrographs of chromatids
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.
The spindle checkpoint, or SAC (for spindle assembly checkpoint), also known as the mitotic checkpoint, is a cellular mechanism responsible for detection of: correct assembly of the mitotic spindle; attachment of all chromosomes to the mitotic spindle in a bipolar manner; congression of all chromosomes at the metaphase plate.
This diagram depicts the organization of a typical mitotic spindle found in animal cells. Chromosomes are attached to kinetochore microtubules via a multiprotein complex called the kinetochore . Polar microtubules interdigitate at the spindle midzone and push the spindle poles apart via motor proteins.
A diagram of the mitotic phases. Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two nuclei. [8] During the process of mitosis the pairs of chromosomes condense and attach to microtubules that pull the sister chromatids to opposite sides of the cell. [9]
Just before mitosis starts, the preprophase band forms as a dense band of microtubules around the phragmosome and the future division plane just below the plasma membrane. It encircles the nucleus at the equatorial plane of the future mitotic spindle when dividing cells enter the G2 phase of the cell cycle after DNA replication is complete.