(Phys.org) —At the cellular level, the mitotic spindle apparatus is arguably the most complicated piece of machinery in existence. Its basic function is to isolate and separate the chromosomes during cell division. A group ...
When an egg cell is being formed, the cellular machinery which separates chromosomes is extremely imprecise at fishing them out of the cell's interior, scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, ...
Cell & Microbiology
Aug 18, 2011
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In a study to be published in the journal Nature, two Dartmouth researchers have found that the protein cyclin A plays an important but previously unknown role in the cell division process, acting as a master controller to ...
Cell & Microbiology
Sep 11, 2013
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During cell division in a mother cell, the 23 chromosomes that carry the human genome must be first copied and later delivered to two newly forming daughter cells. At least in healthy cells, the result is astonishingly flawless, ...
Molecular & Computational biology
Apr 8, 2022
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Starting as a single cell, organisms undergo millions of generations of divisions to ultimately generate the bones, heart, brain and other components that make up a living being. The mainspring within this intricate process ...
Cell & Microbiology
Jan 6, 2021
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(PhysOrg.com) -- University of Washington (UW) researchers are helping to write the operating manual for the nano-scale machine that separates chromosomes before cell division. The apparatus is called a spindle because it ...
Cell & Microbiology
Mar 6, 2009
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Researchers led by Osaka University used cryogenic electron microscopy to analyze the atomic structure of the centromeric region of the chromosome, essential for cell division. A protein called CENP-A marks the centromere; ...
Cell & Microbiology
Feb 6, 2023
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The protein complex responsible for the distribution of chromosomes during cell division is assembled in the transition regions between heterochromatin and euchromatin.
Cell & Microbiology
Jul 5, 2011
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Centromeres are specialised regions of the genome, which can be identified under the microscope as the primary constriction in X-shaped chromosomes. The cell skeleton, which distributes the chromosomes to the two daughter ...
Cell & Microbiology
Nov 3, 2011
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During the process of cell division, chromosomes must be distributed equally between the two emerging daughter cells. One copy of each chromosome is created and remains glued to the original until threads, called microtubules, ...
Cell & Microbiology
Sep 9, 2016
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The kinetochore ( /kɪˈnɛtəkɔər/) is the protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart.
The kinetochore forms in eukaryotes, assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis.
"Monocentric" organisms, including vertebrates, fungi, and most plants, have a single centromeric region on each chromosome which assembles one kinetochore. "Holocentric" organisms, such as nematodes and some plants, assemble a kinetochore along the entire length of a chromosome.
The kinetochore contains two regions:
Kinetochores start, control and supervise the striking movements of chromosomes during cell division. During mitosis, which occurs after chromosomes are duplicated during S phase, two sister chromatids are held together each with its own kinetochore which face in opposing directions and attach to opposite poles of the mitotic spindle. Following the transition from metaphase to anaphase, the sister chromatids separate from each other, and the individual kinetochores on each chromatid drive their movement to the spindle poles that will define the two new daughter cells. Thus, the kinetochore is essential for the chromosome segregation that is classically associated with mitosis and meiosis.
Even the simplest kinetochores consist of more than 45 different proteins. Many of these proteins are conserved throughout eukaryote species, including a specialized histone H3 variant (called CENP-A or CenH3) which helps the kinetochore associate with DNA. Other proteins in the kinetochore attach it to the microtubules (MTs) of the mitotic spindle. There are also motor proteins, including both dynein and kinesin, which generate forces that move chromosomes during mitosis. Other proteins, such as MAD2 monitor the microtubule attachment as well as the tension between sister kinetochores and activate the spindle checkpoint to arrest the cell cycle when either of these is absent.
In summary, kinetochore functions include anchoring of chromosomes to MTs in the spindle, verification of anchoring, activation of the spindle checkpoint and participation in force generation to propel chromosome movement during cell division.
On the other hand, MTs are metastable polymers made of α- and β-tubulin, alternating between growing and shrinking phases, a phenomenon known as "dynamic instability". MTs are highly dynamic structures, whose behavior is integrated with kinetochore function to control chromosome movement and segregation.
This text uses material from Wikipedia, licensed under CC BY-SA
