Problem: When we discussed Angelman syndrome (AS), we stated that only UBE3A protein was expressed in the brain. If a de novo UBE3A paternal mutation was transmitted to his son, then son could transmit this silent mutation to his daughter, who would have a 50% risk of having a child (male or female) with AS. AS, like Prader Willi Syndrome (PWS), is usually caused by uniparental disomy (UPD) of Chromosome 15.
a. Explain why Prader Willi syndrome (PWS) is more common than AS?