Angelman synrome (AS) is a neuro-genetic disorder named after a British pediatrician, Dr. Harry Angelman, who first described the syndrome in 1965. AS is characterized by intellectual and developmental delay, speech impediment, sleep disturbance, unstable jerky gait, seizures, hand flapping movements, frequent laughter/smiling and usually a happy demeanour. AS is a classic example of genetic imprinting caused by deletion or inactivation of critical genes on the maternally inherited chromosome 15. The sister syndrome is called Prader-Willi syndrome, and is caused by loss of paternal imprinting pattern on paternally-inherited alleles. Usually this is determined by maternal genes.