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Summary. Uniparental disomy (UPD) is the presence, in a diploid individual, of a chromosome pair that derives from only one parent. In general the mechanism of formation of UPD is based on the correction of aneuplody derived from meiotic or mitotic errors. UPD almost all chromosmes have been documented but preponderance of maternal versus paternal disomy (3:1) have been observed. This difference can be explained with the frequency of aneuploidy in the female gametogenesis. After over 20 years of studies since the concept of UPD was introduced unusual and unexplained observations on the clinical expression some of genetic disorders are now clear. The phenotype in such disorders is determined by genomic imprinting disturbances and nonmendelian inheritance of monogenic recesive traits due to the loss of heterosigosity in UPD cases. Undetected mosaicism may also reflect an abnormal phenotype. The mechanisms of UPD formation, present knowledge on the frequency, risk factors and clinical consequences of uniparental disomy are presented.
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The Editorial Board
Andrzej Łukaszyk - przewodniczący, Zofia Bielańska-Osuchowska, Szczepan Biliński, Mieczysław Chorąży, Aleksander Koj, Włodzimierz Korochoda, Leszek Kuźnicki, Aleksandra Stojałowska, Lech Wojtczak

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