Uniparental disomy

Uniparental disomy (pronunciation: yoo-ni-puh-REN-tl di-SOH-mee) is a rare genetic condition that 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. The term is derived from the Latin uni meaning 'one', parentalis meaning 'parental', and disomy meaning 'two bodies'.

Definition

Uniparental disomy (UPD) is a situation in which both copies of a chromosome come from the same parent, instead of one copy coming from the mother and one from the father. This can occur as a random event during the formation of egg or sperm cells or may happen in early fetal development.

Types

There are two types of uniparental disomy: Heterodisomy and Isodisomy. Heterodisomy (pronounced: het-ero-di-SOH-mee) occurs when a person receives two different copies of a chromosome from one parent. Isodisomy (pronounced: iso-di-SOH-mee) occurs when a person receives two copies of the same chromosome from one parent.

Causes

Uniparental disomy can be caused by errors in meiosis, the process that produces egg and sperm cells. It can also occur due to a phenomenon known as trisomic rescue, where an embryo starts off with three copies of a chromosome but one is lost, leaving two copies from the same parent.

Related Terms

• Genetic Imprinting
• Prader-Willi Syndrome
• Angelman Syndrome

See Also

• Genetics
• Chromosome
• Meiosis

External links

• Medical encyclopedia article on Uniparental disomy
• Wikipedia's article - Uniparental disomy

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