Similarly, duplications of the wild-type SNCA gene result in a 1.5-fold elevation of SNCA expression and a slightly later onset of heritable PD that is characterized by a lower penetrance rate and a ‘milder’ phenotype than for the triplication [6]–[9], demonstrating the dose-dependent effect of SNCA on disease presentation. The gene discussed is SNCA; the disease is Parkinson disease.