Trisomy

trisomy
the diploid condition plus one extra chromosome: 2n + 1
Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row ...

Down Syndrome (Trisomy 21)
Down syndrome is a genetic disease resulting from a chromosomal abnormality. An individual with Down syndrome inherits all or part of an extra copy of Chromosome 21.

Trisomy 18 or Edward's Syndrome, is the second most common trisomy after Down's Syndrome. Edward's Syndrome occurs when three sets (trisomy) of chromosome 18 occur.

Trisomy 18 or Edwards Syndrome (named after John H. Edwards, who first described the syndrome in 1960) is a genetic disorder. It is the most common autosomal trisomy after Down Syndrome.
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trisomy A condition where a cell has an extra chromosome.
trophoblast The outer layer of cells of a blastocyst that adhere to the endometrium during implantation.

Trisomy having three copies of a single chromosome
Tumour suppresser gene A gene which if inactivated by mutation allows uncontrolled cellular proliferation. Contrast with oncogene.

Trisomy Possessing three copies of a particular chromosome instead of the normal two copies.
See also: cell, gene, gene expression, chromosome
Updated 26-Apr-07
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Trisomy 18 (Edward Syndrome)
Trisomy 18 is associated with mental and physical retardation, skull and facial abnormalities, defects in all organ systems, and poor muscle tone.
Mean survival is 2 to 4 months.

Trisomy
The term proposed by Blakeslee (1922) to describe an otherwise diploid individual which has one of the chromosomes represented three times instead of twice. Caused by nondisjunction during cell division.
Related Terms:
Diploid ...

KARYOTYPE OF TRISOMY 21 FEMALE
The rate of non disjunction is correlated with maternal age. The probability of a woman having a fetus with a chromosome defect increases with age.

Advanced maternal age -- women over age 34 (age 35 at delivery) at increased risk for nondisjunction trisomy in fetus. Alcoholism -- a chronic and progressive condition characterized by the inability to control the consumption of alcohol.

[More] DNase I DollyFirst mammal (a sheep) cloned from an adult cell [more] Domains, protein Dopamine[as hormone] [as neurotransmitter] Dose-response relationships Double-stranded breaks (DSBs) in DNA Doubling times Down syndrome (trisomy 21) ...

In humans, nondisjunction is most often associated with the 21st chromosome, producing a disease known as Down's syndrome (also referred to as trisomy 21).

Trisomy 21, exception leading to Downs syndrome
Sex chromosomes
Turner syndrome: monosomy X
Klinefelter syndrome: XXY
Translocation and deletion: transfer of a piece of one chromosome to another or loss of fragment of a chromosome.

nondisjunction. Failure of a pair of homologous chromosomes to separate during meiosis, leading to one gamete with n + 1 chromosomes (see trisomy) and another gamete with n _ 1 chromosomes.

Aneuploidy
A chromosome number that is not an exact multiple of the haploid number. Usually refers to an absence (monosomy) or an extra copy (trisomy) of a single chromosome.

Apart from being an important cause of uniparental disomy, it may cause trisomy 21 (Down's syndrome) in the offspring.

Trisomy 3 copies of a particular chromosome (normally we have only 2.)
tRNA See transfer RNA.

See also: Chromosome, Chromosomes, Human, Cell, Trans