UBE3A and autism: Individuals with an additional maternal copy of UBE3A (dup15), due to duplication of the 15q11.2–11.3 chromosomal region, and those with two extra copies from an isodicentric chromosome 15 (idic15) both display autism penetrance, with the two extra copies resulting in a more severe phenotype (Borgatti et al., 2001; Hogart et al., 2010).