Tags: Disease.
Uniparental disomy (UPD) occurs when a person receives two copies of a chromosome or of part of a chromosome from one parent and no copies from the other parent. UPD can be the result of heterodisomy in which a pair of non-identical chromosomes are inherited from one parent (an earlier stage meiosis I error) or isodisomy in which a single chromosome from one parent is duplicated (a later stage meiosis II error).