Uniparental disomy (UPD) describes a condition in which both homologs of a chromosome pair are derived from the same parent.  UPD can be associated with phenotypic abnormalities if:

  • the chromosome or chromosome segment involved carries genes that are imprinted.  Genomic imprinting refers to the differential expression of alleles as determined by the parental origin of the allele.
  • homozygosity due to uniparental isodisomy results in the expression of an autosomal recessive condition from a single carrier parent.

UPD has been demonstrated in patients with Prader-Willi syndrome (UPD15mat) and Angelman syndrome (UPD15pat). We offer UPD testing of chromosome 15 by microsatellite analysis, which compares microsatellite markers from both parents and the child or fetus. In order for UPD to be determined, a significant number of informative microsatellite markers must be present. Although testing is possible if only one parent is available, the chance of obtaining a sufficient number of informative markers is decreased.

Prenatal UPD studies are appropriate following the detection of a mosaic trisomy or a marker chromosome in a prenatal sample.  UPD analysis is also considered when a prenatal test is performed to rule out the possibility that the fetus has inherited an unbalanced translocation from a parent carrying a balanced rearrangement and for pregnancies affected with a de novo translocation. 

2 - 4 weeks
CPT Code 
Test Code 
Test Methods 
Microsatellite analysis
Specimen Types Accepted 
Cultured Cells
Extracted DNA
Additional Information 
Requires samples from both parents
The cost for prenatal UPD is $740