Prader-Willi Syndrome is caused by the loss of function of genes in a specific region of the paternal chromosome 15. This can occur through three main mechanisms: 1. A deletion in the paternal chromosome 15q11-q13 region. 2. Maternal uniparental disomy (UPD), where the child inherits two copies of chromosome 15 from the mother and none from the father. 3. Imprinting defects that result in the paternal genes being incorrectly silenced.
