WordNet

chrosomal abnormality in which there is one more than the normal number of chromosomes in a cell

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/06/23 00:36:17」(JST)

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A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two.^[1] A trisomy is a type of aneuploidy (an abnormal number of chromosomes).

Description and causes

Most organisms that reproduce sexually have pairs of chromosomes in each cell, with one chromosome inherited from each parent. In such organisms, a process called meiosis creates cells called gametes (eggs or sperm) that have only one set of chromosomes. The number of chromosomes is different for different species. Humans have 46 chromosomes (i.e. 23 pairs of chromosomes). Human gametes have only 23 chromosomes.

If the chromosome pairs fail to separate properly during cell division, the egg or sperm may end up with a second copy of one of the chromosomes. (See non-disjunction.) If such a gamete results in fertilization and an embryo, the resulting embryo may also have an entire copy of the extra chromosome.

Terminology

The number of chromosomes in the cell where trisomy occurs is represented as, for example, 2n+1 if one chromosome shows trisomy, 2n+1+1 if two show trisomy, etc.^[2]

"Full trisomy", also called "primary trisomy",^[2] means that an entire extra chromosome has been copied. *"Partial trisomy" means that there is an extra copy of part of a chromosome.
"Secondary trisomy" - the extra chromosome has quadruplicated arms (the arms are identical; it is an "isochromosome").^[2]
"Tertiary trisomy" - the extra chromosome is made up of copies of arms from two other chromosomes.^[2]

Trisomies are sometimes characterised as "autosomal trisomies" (trisomies of the non-sex chromosomes) and "sex-chromosome trisomies." Autosomal trisomies are described by referencing the specific chromosome that has an extra copy.^{[citation needed]} Thus, for example, the presence of an extra chromosome 21, which is found in Down syndrome, is called trisomy 21.

Human trisomy

Karyotype of a human with Trisomy 21 (Down syndrome)

Trisomies can occur with any chromosome, but often result in miscarriage, rather than live birth. For example, Trisomy 16 is the most common trisomy in human pregnancies, occurring in more than 1% of pregnancies; only those pregnancies in which some normal cells occur in addition to the trisomic cells, or mosaic trisomy 16, survive.^[3] This condition, however, usually results in spontaneous miscarriage in the first trimester.

The most common types of autosomal trisomy that survive to birth in humans are:

Trisomy 21 (Down syndrome)
Trisomy 18 (Edwards syndrome)
Trisomy 13 (Patau syndrome)
Trisomy 9
Trisomy 8 (Warkany syndrome 2)
Trisomy 22

Of these, Trisomy 21 and Trisomy 18 are the most common. In rare cases, a fetus with Trisomy 13 can survive, giving rise to Patau syndrome. Autosomal trisomy can be associated with birth defects, intellectual disability and shortened life expectancy.

Trisomy of sex chromosomes can also occur and include:^[4]

XXX (Triple X syndrome)
XXY (Klinefelter syndrome)
XYY

Compared to trisomy of the autosomal chromosomes, trisomy of the sex chromosomes normally has less severe consequences. Individuals may show few or no symptoms and have a normal life expectancy.^[4]

References

^ "CRC - Glossary T". Retrieved 2007-12-23.
^ ^a ^b ^c ^d Rieger, R.; Michaelis, A.; Green, M.M. (1968). A glossary of genetics and cytogenetics: Classical and molecular. New York: Springer-Verlag. ISBN 9780387076683.
^ Hassold, T; Merrill, M; Adkins, K; Freeman, S; Sherman, S (1995). "Recombination and maternal age-dependent nondisjunction: molecular studies of trisomy 16". American Journal of Human Genetics 57 (4): 867–74. PMC 1801507. PMID 7573048.
^ ^a ^b O'Connor, Clare (2008). "Chromosomal Abnormalities: Aneuploidies". Nature Education 1 (1): 172.

UpToDate Contents

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1. 先天性の細胞遺伝学的異常 congenital cytogenetic abnormalities
2. First-trimester combined test and integrated tests for screening for Down syndrome and trisomy 18
3. 胎児異数性に関連する超音波所見 sonographic findings associated with fetal aneuploidy
4. Prenatal screening for common aneuploidies using cell-free DNA
5. 遺伝的変異の概要 overview of genetic variation

English Journal

Demonstration of uniparental-isodisomy on chromosome 22q11.2 in a patient with childhood schizophrenia and facial dysmorphology by whole-genome analysis.

Cogulu O, Pariltay E, Durmaz AA, Aykut A, Gunduz C, Ozbaran B, Aydin HH, Erermis S, Aydin C, Ozkinay F.
The Journal of neuropsychiatry and clinical neurosciences.J Neuropsychiatry Clin Neurosci.2012 Dec 1;24(1):E13-4.
PMID 22450627

Downregulation of A(1) and A(2B) adenosine receptors in human trisomy 21 mesenchymal cells from first-trimester chorionic villi.

Gessi S, Merighi S, Stefanelli A, Mirandola P, Bonfatti A, Fini S, Sensi A, Marci R, Varani K, Borea PA, Vesce F.SourceDepartment of Clinical and Experimental Medicine, Pharmacology Unit and Interdisciplinary Center for the Study of Inflammation, University of Ferrara, Via Fossato di Mortara 17-19, 44100 Ferrara, Italy.
Biochimica et biophysica acta.Biochim Biophys Acta.2012 Nov;1822(11):1660-70. doi: 10.1016/j.bbadis.2012.07.013. Epub 2012 Jul 31.
Human reproduction is complex and prone to failure. Though causes of miscarriage remain unclear, adenosine, a proangiogenic nucleoside, may help determine pregnancy outcome. Although adenosine receptor (AR) expression has been characterized in euploid pregnancies, no information is available for ane
PMID 22867902

Japanese Journal

症例 14トリソミーが見出されたLiner and Whorled Nevoid Hypermelanosisの1例

中川恵子,芳賀恒夫,布施恵理 [他]
皮膚科の臨床 54(7), 999-1002, 2012-07
NAID 40019379631

症例報告一期的根治術を施行した18トリソミー合併食道閉鎖症(C型)の極・超低出生体重児の2例

坂本浩一,野口啓幸,前出喜信 [他]
日本小児外科学会雑誌 48(4), 781-785, 2012-06
NAID 40019370513

Related Pictures

★リンクテーブル★

リンク元	「トリソミー」「trisomic」「三染色体性」
拡張検索	「trisomy 8 mosaicism」

「トリソミー」

Trisomy
	Example of Trisomy 21 detected via qPCR Short Tandem Repeat assay
Classification and external resources
ICD-10	Q90-Q92; Q97-Q98
MeSH	D014314

　　[★]

英: trisomy
同: 三染色体、三染色体性

first aid step1 2006 p.110

染色体が3本ある

トリソミー

		trisomy 21	trisomy 18	trisomy 13
		Down syndrome	Edwards' syndrome	Patau's syndrome
		1:700	1:8000	1:6000
頭部	精神遅滞	◯	◯	◯
	小頭症			◯
	後頭部隆起		◯
	小眼球症			◯
顔面	全前脳胞症			◯
	内眼角贅皮、扁平顔貌	◯
	低位耳介		◯
	口唇口蓋裂			◯
	小顎症		◯
頚部	短い首		◯
頚部	頚の皮が多い	◯
手	猿線	◯
	重畳手指		◯
	多指症			◯
心	心奇形	◯	◯	◯
消化器	消化管狭窄	◯
消化器	臍ヘルニア	◯		◯
泌尿器	腎形成不全		◯
泌尿器	腎不全			◯
股関節	股関節外転の制限		◯
足	揺り椅子状の足底		◯	◯
足	第1趾と第2趾の離解	◯
筋	低筋緊張	◯