Uniparental disomy in neurologic diseases
Uniparental disomy ( UPD ) occurs when an individual carries two copies of a chromosome, or part of a chromosome, from the same parent and no copies from the other parent.
UPD can be the result of heterodisomy or isodisomy. In heterodisomy, a pair of nonidentical chromosomes are inherited from the same parent, the result of a meiosis I error.
Heterodisomy is essentially benign. In isodisomy, a single chromosome from one parent is duplicated during a meiosis II error. In contrast to heterodisomy, isodisomy may lead to the duplication of lethal or deleterious recessive mutations and has the potential to cause pathogenic phenotypes.
Uniparental inheritance of imprinted genes can also cause phenotypical abnormalities.
The best-known examples of neurologic diseases involving UPD include Prader–Willi syndrome and Angelman syndrome.