Angelman syndrome affects one in every 10,000 to 12,000 births. Prader-Willi syndrome, at one in 12,000-15,000 births, is even rarer. Rett syndrome affects one in every 12,500 female births. Clearly, ...

We each get two copies of every gene - one copy from each of our parents. But what happens when one of these genes has been "turned off", or imprinted, and the remaining gene is defective?

Prader-Willi and Angelman syndromes are rare genetic disorders affecting about 1 in 10,000 to 30,000 and 1 in 12,000 to ...