Practice question

Angelman syndrome results from loss of maternal UBE3A gene expression specifically in neurons due to deletion, uniparental disomy, or imprinting defect affecting chromosome fifteen q eleven to thirteen region. UBE3A is imprinted in brain, expressed only from maternal allele because paternal copy silenced epigenetically by antisense transcript. Absence of maternal contribution causes neurodevelopmental disorder characterized by seizures, ataxia, and happy demeanor. Prader-Willi syndrome arises from loss of paternal contribution in same region, illustrating differential parental expression. Thus Angelman exemplifies genomic imprinting disorder.