SNCA and Alzheimer disease: Genetic testing have identified numerous mutations in relation to JP, such as mutations in the SNCA gene (located on chromosome 4q22.1) and GCH1 gene (located on chromosome 14q22.2) with autosomal dominant (AD) inheritance, PRKN (PARK2) gene (located on chromosome 6q26), TH gene (located on chromosome 11p15.5) and DJ1 gene (located on chromosome 1p36.32) with autosomal recessive (AR) inheritance, PINK1 gene (located on chromosome 1p36.12) with either AD or AR inheritance (Morris and Lim, 2004).