- Uniparental disomy
Infobox_Disease
Name = Uniparental disomy
Caption =
DiseasesDB =
ICD10 = ICD10|Q|99|8|q|90
ICD9 =
ICDO =
OMIM =
MedlinePlus =
eMedicineSubj =
eMedicineTopic =
MeshID =Uniparental disomy (UPD) occurs when a person receives two copies of a
chromosome , or part of a chromosome, from one parent and no copies from the other parent. cite journal |author=Robinson WP |title=Mechanisms leading to uniparental disomy and their clinical consequences |journal=Bioessays |volume=22 |issue=5 |pages=452–9 |year=2000 |month=May |pmid=10797485 |doi=10.1002/(SICI)1521-1878(200005)22:5<452::AID-BIES7>3.0.CO;2-K |url=http://dx.doi.org/10.1002/(SICI)1521-1878(200005)22:5<452::AID-BIES7>3.0.CO;2-K]Pathophysiology
UPD can occur as a random event during the formation of egg or
sperm cells or may happen in early fetal development. It can also occur duringtrisomic rescue .* When the child receives the "(two)
homologous chromosomes " (inherited from both grandparents) from one parent, this is called an heterodisomic UPD.Heterodisomy (Heterozygous ) indicates ameiosis I error.* When the child receives, "two (identical) replica copies of a single
homolog of achromosome ", this is called an isodisomic UPD.Isodisomy (homozygous ) indicates either ameiosis II error orpostzygotic duplication .Phenotype
Most occurrences of UPD result in no
phenotypical anomalies. However, if the UPD causing event happens duringmeiosis II, thegenotype may include identical copies of the uniparental chromosome (isodisomy), leading to the manifestation of rarerecessive disorders. UPD should be suspected in an individual manifesting a recessive disorder, where only one parent is a carrier.Uniparental inheritance of imprinted genes can also result in
phenotypical anomalies. Few imprinted genes have been identified, however uniparental inheritance of an imprinted gene can result in the loss of gene function which can lead to delayed development, mental retardation, or other medical problems.* The most well-known conditions include
Prader-Willi syndrome andAngelman syndrome . Both of these disorders can be caused by UPD or other errors in imprinting involving genes on the long arm ofchromosome 15 .
* Other conditions, such asBeckwith-Wiedemann syndrome , are associated with abnormalities of imprinted genes on the short arm ofchromosome 11 .
*Chromosome 14 is also known to cause particular symptoms such as skeletal abnormalities,mental retardation and joint contractures among others. [OMIM2|608149] [DiseasesDB2|32320]All chromosomes
Occasionally, all chromosomes will be inherited from one parent, due to either a sperm fertilizing an empty egg and duplicating itself, or a diploid egg that is not fertilized. The effect is similar to
triploidy , with either amolar pregnancy with no embryo if only paternal genes are present, or an embryo with no placenta if only maternal genes are present. Neither condition ever results in a liveborn infant.History
The first clinical case of UPD was reported in 1991 and involved a girl with cystic fibrosis and unusually short stature who carried two copies of maternal
chromosome 7 . Since 1991, out of the 47 possible disomies, 29 have been identified among individuals ascertained for medical reasons. This includesChromosome 2, 5-11, 13-16, 21 and 22. [ [http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=GB&Expert=228 Orphanet: Search a disease ] ]References
External links
* [http://www.medgen.ubc.ca/robinsonlab/mosaic.htm Uniparental disomy] (University of British Columbia)
"This article incorporates public domain text from [http://ghr.nlm.nih.gov The U.S. National Library of Medicine] "
Wikimedia Foundation. 2010.