A micronucleus is a small nucleus that forms whenever a chromosome or a fragment of a chromosome is not incorporated into one of the daughter nuclei during cell division. It usually is a sign of genotoxic events and chromosomal instability. Micronuclei are commonly seen in cancerous cells and may indicate genomic damage events that can increase the risk of developmental or degenerative diseases.[1]
Micronuclei form during anaphase from lagging acentric chromosomes or chromatid fragments caused by incorrectly repaired or unrepaired DNA breaks or by nondisjunction of chromosomes. This improper segregation of chromosomes may result from hypomethylation of repeat sequences present in pericentromeric DNA, irregularities in kinetochore proteins or their assembly, a dysfunctional spindle apparatus, or flawed anaphase checkpoint genes.[2] Micronuclei can contribute to genome instability by promoting a catastrophic mutational event called chromothripsis.[3] Many micronucleus assays have been developed to test for the presence of these structures and determine their frequency in cells exposed to certain chemicals or subjected to stressful conditions.
The term micronucleus may also refer to the smaller nucleus in ciliate protozoans, such as the Paramecium. In mitosis it divides by fission, and in conjugation a pair of gamete micronuclei undergo reciprocal fusion to form a zygote nucleus, which gives rise to the macronuclei and micronuclei of the individuals of the next cycle of fission.[4]
^"Micronucleus". ntp.niehs.nih.gov. Archived from the original on 2016-10-18. Retrieved 2016-10-14.
^Fenech, M.; Kirsch-Volders, M.; Natarajan, A. T.; Surralles, J.; Crott, J. W.; Parry, J.; Norppa, H.; Eastmond, D. A.; Tucker, J. D. (2011-01-01). "Molecular mechanisms of micronucleus, nucleoplasmic bridge and nuclear bud formation in mammalian and human cells". Mutagenesis. 26 (1): 125–132. doi:10.1093/mutage/geq052. ISSN 0267-8357. PMID 21164193.
^Umbreit, Neil T.; Zhang, Cheng-Zhong; Lynch, Luke D.; Blaine, Logan J.; Cheng, Anna M.; Tourdot, Richard; Sun, Lili; Almubarak, Hannah F.; Judge, Kim; Mitchell, Thomas J.; Spektor, Alexander (2020-04-17). "Mechanisms generating cancer genome complexity from a single cell division error". Science. 368 (6488): eaba0712. doi:10.1126/science.aba0712. ISSN 0036-8075. PMC 7347108. PMID 32299917.
^One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Micronucleus". Encyclopædia Britannica. Vol. 18 (11th ed.). Cambridge University Press. p. 391.
A micronucleus is a small nucleus that forms whenever a chromosome or a fragment of a chromosome is not incorporated into one of the daughter nuclei during...
There is a chance of more than one micronucleus forming when more genetic damage has happened. The micronucleus test is used as a tool for genotoxicity...
The latter is generated from the micronucleus by amplification of the genome and heavy editing. The micronucleus passes its genetic material to offspring...
The two cells exchange a micronucleus. The cells then separate. The micronuclei in each cell fuse, forming a diploid micronucleus. Mitosis occurs three times...
maintains two distinct nuclear genomes, the micronucleus and the macronucleus. The macronucleus and micronucleus are located in the same cytoplasm, however...
compact micronucleus). As in other ciliates, individuals cannot survive without the macronucleus and cannot reproduce without the micronucleus. Paramecia...
divisions and contribute to the development of a cancer cell. Although the micronucleus model is appropriate, other factors are likely to contribute towards...
ciliates being the metazoan ancestor. Ciliates have two types of nuclei: a micronucleus which is used as germline nucleus and a macronucleus which regulates...
ciliates: a macronucleus for normal metabolic control and a separate micronucleus that undergoes meiosis. Examples of such ciliates are Paramecium and...
Stanković, M (2009). "Antioxidant properties of raspberry seed extracts on micronucleus distribution in peripheral blood lymphocytes". Food Chem Toxicol. 47...
long, with a wide oral groove, two contractile vacuoles, and a single micronucleus as well as a single macronucleus. P. bursaria is the only species of...
numerical aberrations of the genetic material. This is similar to the micronucleus test and chromosome aberration assay, which detect structural and numerical...
The micronucleus test is another type of assay that uses gut cells to observe clastogens, and there are a few different types. The micronucleus test...
conjugant pairs. This pairing can last up to 12 hours, during which the micronucleus of each organism will be exchanged. In Paramecium aurelia, a cryptic...
is the first description of gene duplication and amplification in the micronucleus of ciliates. Additionally, it appears that the duplication of the mutant...
visible. The macronucleus is long and sausage-shaped, and the spherical micronucleus is nested next to it, often hidden by the macronucleus. The opening,...
maintain a balanced genome after generations of divisions is unknown. Micronucleus Mochizuki K (2010-07-15). "DNA rearrangements directed by non-coding...
They have a bigger, non-germline macronucleus and a small, germline micronucleus in each cell at the same time and these two carry out different functions...
of n=6, the broad bean has a high DNA content, making it easy for a micronucleus test of its root tips to recognize genotoxic compounds. A lectin from...
rejuvenation is due to repair of DNA damage during meiosis that occurs in the micronucleus during conjugation or automixis and reestablishment of the macronucleus...
nuclear dimorphism): a micronucleus used for inheritance, and a macronucleus, which controls the metabolism. The micronucleus contains the entirety of...
of cell nuclei, a large, somatic macronucleus and a small, germline micronucleus. Both exist in a single cell at the same time and carry out different...
nuclei. Ciliates have cells that contain two nuclei: a macronucleus and a micronucleus. The schizont of apicomplexan parasites is a form of a coenocyte (i.e...
uncinata has cilia covering its body and a dual nuclear structure, the micronucleus and macronucleus. Unlike some other ciliates, C. uncinata contains millions...
exposure induces genome damage measured using the cytokinesis-block micronucleus cytome assay and aneuploidy in human B lymphoblastoid cell lines". Mutagenesis...
the cell. Inside, there is a curved, transverse macronucleus and round micronucleus near it. The similar genus Pseudovorticella is practically indistinguishable...
by assays for genotoxicity such as the comet assay, cytokinesis-block micronucleus test and chromosome aberrations test. In humans, this damage can happen...
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