Uniparental Disomy:

Prader-Willi Syndrome & Angelman Syndrome

What is uniparental disomy?

We inherit one copy of each chromosome pair from our biological mother, and the other copy of the chromosome pair from our biological father.

Uniparental disomy is when two copies of a chromosome come from the same parent, instead of one copy coming from the mother and one copy coming from the father.

Angelman syndrome and Prader-Willi syndrome are examples of disorders caused by uniparental disomy.

What is Angelman syndrome?

People with Angelman syndrome have mental retardation, severe speech problems, stiff arm movements and a stiff, uncoordinated walk. They may have seizures and often have inappropriate outbursts of laughter.

Angelman syndrome is when a baby inherits both copies of a section of chromosome No. 15 from the father--rather than one from the mother and one from the father.

What is Prader-Willi syndrome?

Prader-Willi syndrome is when a baby inherits both copies of a section of chromosome No. 15 from the mother.

Babies born with Prader-Willi syndrome have poor muscle tone and a weak cry. They initially are slow feeders and appear undernourished. The feeding problems improve after infancy.

Usually between 2 to 4 years of age, the child becomes obsessed with food and is unable to control their appetite. The overeating often results in rapid weight gain and obesity. Individuals with Prader-Willi syndrome are mentally retarded and are shorter than the average adult.

Consult your physician or genetic counselor for more information regarding uniparental disomies.