Uniparental disomy is a chromosome abnormality where a pair of chromosomes only have DNA from one parent and are miss DNA from the other parent. This abnormality happens during mitosis.

A defect on maternal chromosome 15 will cause the sundrome. Since the paternal copy, which is most likely normal is silenced, it makes no difference.

Uniparental disomy will also result in the syndrome.

No. However, if the maternal copy of chromosome 15 has a mutation on a specific gene, angelman's results. Also, getting two copies of chromosome 15 from the father results in angelman's (Paternal uniparental disomy).

Eric Engel has written:

'Genomic imprinting and uniparental disomy in medicine' -- subject(s): Chromosome abnormalities, Genetic disorders, Genomic imprinting

Most cases of Angelman syndrome are not inherited, particularly those caused by a deletion in the maternal chromosome 15 or by paternal uniparental disomy. These genetic changes occur as random events during the formation of reproductive cells (eggs and sperm) or in early embryonic development. Affected people typically have no history of the disorder in their family.