Figure 2.

Illustration of the different genotypes involved in PWS and AS. In typical development, paternally imprinted genes are expressed only from the maternally derived chromosome and vice versa. In PWS and AS, de novo mutations lead to a lack of expression for paternally or maternally expressed genes in the 15q11q-q13 chromosome region. However, the dosage of paternally and maternally expressed genes in the chromosome region varies depending on the genotype as shown above.