What genetic abnormality is associated with Prader-Willi Syndrome?

Prader-Willi Syndrome is specifically linked to an abnormality on chromosome 15 related to paternal genetic contribution. This condition arises due to the loss of function of genes on the paternal allele of chromosome 15, often due to a deletion of a section of this chromosome or uniparental disomy where both copies of chromosome 15 are inherited from the mother, leading to the absence of the paternal genes needed for normal development.

The presence of this genetic abnormality on the paternal side is critical, as the corresponding genes from the maternal side are normally imprinted (silenced), meaning they do not express their function. This unique mechanism underlies many of the characteristics of Prader-Willi Syndrome, such as hyperphagia, obesity, developmental delay, and hypotonia, emphasizing the importance of the genetic contribution from the paternal side in the syndrome.