Angelman Syndrome

This neurological disorder is caused by a deletion or mutation on the mother's contribution to the 15th chromosome. People with this condition have developmental delays but are generally happy and friendly. They enjoy certain sounds such as flowing water and crackling paper. They have a tendency to make big flapping motions with their hands. They are sensitive to high temperatures. Many of them can learn to perform simple tasks on their own.
Here is an excellent site about Angelman Syndrome.
If the deletion or mutation were on the paternal contribution to the 15th chromosome, Prader-Willi syndrome would result. People with this condition tend to be small in stature and suffer from polyphagia. They also suffer from developmental disabilities.