Department of Pediatrics Division of Genetics and Metabolism

The diagrams below illustrate, for a pair of chromosomes, how pairing and subsequent crossing over, followed by a meiotic error with subsequent rescue, can generate uniparental disomy. The UPD chromosomes can have areas of isodisomy in either the centromeric or telomeric regions, depending on whether a meiosis I or a meiosis II defect occurred. These regions of isodisomy may be detectable by microarray SNP analysis.

Normal meiosis


UPD due to meiosis 1 defect


UPD due to Meiosis II defect