Two patients with ASD and Angelman syndrome, one secondary to a maternal deletion (family ASD 3) and the other to a paternal uniparental disomy (family ASD 4). A. Microsatellites D15S817 and D15S1019 show loss of heterozygosity, with apparently only one allele inherited from the father in both probands. B. Genotyping of five microsatellites in the 15q11-q13 region confirmed the presence of only one allele inherited from the father in Patient 3, indicating a maternal deletion. Patient 4 showed two alleles inherited from the father, indicating a paternal uniparental disomy. C. MPLA showed normal gene dosage in Patient 4, as expected in an uniparental isodisomy, and a 50% reduction in probes ranging from TUBGCP5 to OCA2 in Patient 3, showing a class I deletion of the PWS/AS region.