 2 copies of a specific part of the long arm of chromosome 15q11.2-q13.1 that is mirrored and doubled, with 2 centromeres and 2 DNA satellites.The smallest markers appear to be harmless and they may go undetected.However, if they are large enough to contain a number of important genes, they may result in "idic(15) syndrome" which is characterized by learning disabilities, autism and other neurological symptoms.