trisomy

[′trī‚sō·mē]

(cell and molecular biology)

The presence in triplicate of one of the chromosomes of the complement.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Trisomy

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.

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References in periodicals archive

Meta-analysis of second-trimester markers for trisomy 21. Ultrasound Obstetrics Gynecol 2013;41:247-61.

Segmental duplication-quantitative fluorescent-polymerase chain reaction: An approach for the diagnosis of Down syndrome in India/Segmental duplikasyon-kantitatif floresan polimeraz zincir reaksiyonu: Hindistan'da Down sendromu tanisina yonelik bir yaklasim

Theoretically, the copy number of chromosome 21 in cfDNA with x% fetal fraction would be 2 for a normal fetus and 2 + x% for a fetus with trisomy 21 {[2 X (100 - x) + 3x]/100}.

Noninvasive Prenatal Screening of Fetal Aneuploidy without Massively Parallel Sequencing

An uncommon presentation of stroke in a child with trisomy 21. Pediatr Emerg Care.

RECURRENT STROKES SECONDARY TO MOYAMOYA PHENOMENON IN A CHILD WITH DOWN'S SYNDROME

Of the 80 NIPT results that were reported, 79 (98.8%) indicated a low risk of trisomy 21 and 18.

The value and role of non-invasive prenatal testing in a select South African population

The descriptive study was conducted at Layton Rahmatullah Benevolent Trust (LRBT), Lahore, Pakistan, from October 2013 to April 2014, and comprised children under 15 years of age who had rubella syndrome, herpes simplex, birth trauma, trisomy 21, Nance-Horan syndrome or Lowe's syndrome.

Incidence of environmental and genetic factors causing congenital cataract in Children of Lahore

"It's all based around the number 21 because Laurie has Down's syndrome trisomy 21," he said.

Dad Tim sets himself huge challenge to help Down's charity

Down syndrome (DS) is the most common autosomal abnormality and is the most genetic cause of mental retardation, appearing in about 1 of every 700 newborns.[sup][1],[2] DS can be caused by three types of chromosomal abnormalities: Trisomy 21, translocation, or mosaicism.[sup][2] Trisomy 21 is characterized by the presence of three copies of chromosomes 21, generally resulting from nondisjunction during maternal meiosis whereas the extra chromosome 21 in mosaic DS arises from mitotic nondisjunction in a chromosomally normal zygote.[sup][3] For DS by translocation, the extra chromosome 21 translocated to other chromosomes or to the acrocentric chromosomes of D and G group that is, 13, 14, 15, 21, and 22.[sup][4]

Cytogenetic study of down syndrome in Algeria: Report and review

(3,6,9) Although the laboratories use somewhat different techniques, all of them share very high sensitivity and specificity for detection of trisomy 21 (TABLE 1).

Cell-free DNA screening for women at low risk for fetal aneuploidy

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%).

Aneuploidy screening: newer noninvasive test gains traction

In a prospective, international study published earlier this year that compared cfDNA testing to standard screening for trisomy 21, cfDNA testing identified trisomy 21 in all 38 women with the abnormality, compared to 30 ]of 38 with standard screening.

Pro's and con's of prenatal cell-free DNA testing