One could speculate that PWS/AS, similar to that of ASD, depends on either the involvement of the PWS critical region in the imprinted segment within the 15q11.2-q13 BP2-BP3 region or the involvement of a critical gene, namely, UBE3A in the maternally imprinted segment [43] and in concert with other genes that lie within chromosome 15, not excluding the 15q11.2 BP1-BP2 region genes. The gene discussed is UBE3A; the disease is Prader-Willi syndrome.