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. 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 during trisomic rescue. When the child receives the (two) homologous chromosomes (inherited from both grandparents) from one parent, this is called an heterodisomic UPD. When the child receives, two (identical) replica copies of a single homolog of a chromosome, this is called an isodisomic UPD. Heterodisomy (Heterozygous) indicates a meiosis I error, whereas isodisomy (homozygous) indicates either a meiosis II error or postzygotic duplication. The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) is a coding of diseases and signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or diseases, as classified by the World Health Organization (WHO). ... // Q00-Q99 - Congenital malformations, deformations and chromosomal abnormalities (Q00-Q07) Congenital malformations of the nervous system (Q00) Anencephaly and similar malformations (Q01) Encephalocele (Q02) Microcephaly (Q03) Congenital hydrocephalus (Q04) Other congenital malformations of brain (Q05) Spina bifida (Q06) Other congenital malformations of spinal cord (Q07) Other congenital malformations of nervous... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... Different types of sperm cells: A) spermatozoon (motile), B) spermatium (non-motile), C) fertilization tube with sperm nuclei For other uses, see Sperm (disambiguation). ... Human fetus at eight weeks. ... Trisomy rescue is a genetic phenomenon in which a fertilized ovum containing three copies of a chromosome loses one of these chromosomes to form a normal, diploid chromosome complement. ... A homologous chromosome is one part of two genetically different chromosomes. ... The term homologue or homolog has several meanings: In biology, homologues are structures that are alike because of shared ancestry. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Heterozygote cells are diploid or polyploid and have different alleles at a locus (position) on homologous chromosomes. ... Not to be confused with miosis. ... Homozygote cells are diploid or polyploid and have the same alleles at a locus (position) on homologous chromosomes. ... Not to be confused with miosis. ...

Most occurrences of UPD result in no phenotypical anomalies. However, if the UPD causing event happens during meiosis I, the genotype may include identical copies of the uniparental chromosome (isodisomy), leading to the manifestation of rare recessive disorders. UPD should be suspected in an individual manifesting a recessive disorder, where only one parent is a carrier. The phenotype of an individual organism is either its total physical appearance and constitution, or a specific manifestation of a trait, such as size or eye color, that varies between individuals. ... Not to be confused with miosis. ... This article does not cite its references or sources. ... In genetics, the term recessive gene refers to an allele that causes a phenotype (visible or detectable characteristic) that is only seen in a homozygous genotype (an organism that has two copies of the same allele). ... An asymptomatic carrier (or just carrier), is a person who is infected with an infectious disease or carries the abnormal gene of a recessive genetic disorder, but displays no symptoms. ...

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 and Angelman syndrome. Both of these disorders can be caused by UPD or other errors in imprinting involving genes on the long arm of chromosome 15. Other conditions, such as Beckwith-Wiedemann syndrome, are associated with abnormalities of imprinted genes on the short arm of chromosome 11. Chromosome 14 is also known to cause particular symptoms such as skeletal abnormalities, mental retardation and joint contractures among others.^[1][2] Biological inheritance is the process by which an offspring cell or organism acquires or becomes predisposed to characteristics of its parent cell or organism. ... Genomic imprinting is the phenomenon whereby a small subset of all the genes in the genome are expressed according to their parent of origin. ... The phenotype of an individual organism is either its total physical appearance and constitution, or a specific manifestation of a trait, such as size or eye color, that varies between individuals. ... Prader-Willi syndrome is a genetic disorder, in which seven genes (or some subset thereof) on chromosome 15 are missing or unexpressed (chromosome 15q partial deletion) on the paternal chromosome. ... Angelman Syndrome (AS) is a rare neuro-genetic disorder named after an English pediatrician, Dr. Harry Angelman, who first described the syndrome in 1965. ... Chromosome 15 is one of the 23 pairs of chromosomes in humans. ... Beckwith-Wiedemann syndrome (BWS) is a very rare genetic overgrowth syndrome (prevalence of about 1 in 36,000). ... Chromosome 11 is one of the 23 pairs of chromosomes in humans. ... Chromosome 14 is one of the 23 pairs of chromosomes in humans. ... Mental retardation is a term for a pattern of persistently slow learning of basic motor and language skills (milestones) during childhood, and a significantly below-normal global intellectual capacity as an adult. ...

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 a molar 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. Polyploid (in Greek: πολλαπλόν - multiple) cells or organisms contain more than two copies (ploidy) of their chromosomes. ... Molar pregnancy, sometimes simply referred as mole is a rare abnormal medical condition, a complication of pregnancy inside the category of gestational trophoblastic diseases. ...

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 includes Chromosome 2, 5-11, 13-16, 21 and 22.^[3] Chromosome 7 is one of the 23 pairs of chromosomes in humans. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...

References

External links

• Uniparental disomy (University of British Columbia)

This article incorporates public domain text from The U.S. National Library of Medicine