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Related to Trisomy 18: trisomy 13


(cell and molecular biology)
The presence in triplicate of one of the chromosomes of the complement.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the presence of one or a few nonhomologous extra chromosomes in the chromosome set of a diploid organism. Organisms (or cells) in which one, two, or more chromosomes present themselves as three homologues are called simple trisomics, double trisomics, and so forth. Trisomy is caused by the failure of chromosomes to separate (nondisjunction) during cell division. Some specific severe disorders are the result of trisomy occurring in specific chromosomes.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Typically, trisomy X is a maternal meiosis I error (63% of the time) and trisomy 18 is a maternal meiosis II error 59% of the time [11].
Some obstetricians regard a cleft palate as a major abnormality, while some believe that TOP should be considered for only lethal conditions such as anencephaly and trisomy 18. Late TOP for achondroplasia, hydrocephaly or Down's syndrome could not be justified since they are viable abnormalities, but not lethal.
Caption: EXTRAORDINARY: In contrast to most human trisomies, such as Down syndrome (Trisomy 21) or Edwards syndrome (Trisomy 18), that cause significant intellectual disability and medical complications, X and Y variations cause milder developmental delays.
Trisomy 18.--Genetic testing revealed trisomy 18 in 36 of the 170 fetuses with chromosomal abnormalities (21%).
The fetus was suspected to have chromosomal abnormality, specifically trisomy 18. The parents chose not to carry out prenatal genetic diagnosis.
Of these ambiguously classified samples, 8, 3, and 30 were identified as fetal trisomy 21, fetal trisomy 18, and fetal euploid cases, respectively.
She subsequently had a spontaneous miscarriage, and karyotyping of the products of conception confirmed trisomy 18.
In both live and non-live births, the incidence of trisomy 21 was 5 of 1909 cases (0.3%) and the incidence of trisomy 18 was 2 of 1905 cases (0.1%).
Also known as trisomy 18, it's a life-limiting genetic condition caused by an additional copy of chromosome 18 in some or all of the cells in the body.
However, it has been reported that ectopia cordis may be associated with viral infections, exposure to teratogens and chromosomal disorders including Trisomy 18 and Turner syndrome (2, 6-8).
During the blind clinical test, the foetus' sex was also predicted with 100 per cent accuracy, while it had very high levels of success in detecting trisomy 18 (Edward's syndrome), trisomy 13 (Patau syndrome) and monosomy X (Turner syndrome).