Genetic mechanisms leading to Angelman syndrome

The rectangles represent chromosome 15. Hatched chromosomes have a paternal pattern of gene functioning and DNA methylation; open chromosomes have a maternal pattern. Angelman syndrome is caused by a large deletion of the region of the maternal chromosome that contains UBE3A, or by a DNA sequence change (mutation) in the UBE3A gene inherited from the mother. The condition can also be caused by inheritance of two normal copies of UBE3A from the father, with no copy inherited from the mother. Other AS individuals inherited chromosome 15 from their mother, but that chromosome had the paternal pattern of gene function and DNA methylation.