In Angelman syndrome, the abnormal chromosome is inherited from which parent?

Angelman syndrome is caused by a loss of function of the UBE3A gene, which is located on chromosome 15. In healthy individuals, this gene is expressed from the allele inherited from the mother, while the paternal allele is typically silenced due to genomic imprinting. In Angelman syndrome, the most common cause is a deletion or mutation of the maternal UBE3A gene, leading to a lack of functional protein.

Therefore, the abnormal chromosome that leads to Angelman syndrome is inherited from the mother. This maternal inheritance is essential because without the maternal expression of the UBE3A gene, the neuronal functions that require this protein are compromised, resulting in the symptoms of the syndrome.

The mechanisms behind this syndrome highlight the importance of genomic imprinting, where certain genes are expressed in a parent-of-origin-specific manner. Understanding this parent-specific gene expression illustrates why the maternal origin of the abnormal chromosome is pivotal in Angelman syndrome.