Detection of DA within cytogenetically-distinguishable homologous regions of known parental origin. Genomic coordinates of single copy probes detecting DA within 5 different chromosomal regions are indicated. Schematic of the normal and derivative (der) or inverted (inv) chromosome with homologous target are shown. Specific chromosomes are highlighted (white rectangles), ‘mat’ and ‘pat’ refer to the maternal or paternal origin of the altered homolog, respectively. Brighter probe intensity was recurrently observed on the same homolog for a probe for each cell line. RGS7 probe had greater target accessibility on the der chromosome 11 (paternal, GM10958). CACNA1B had greater target accessibility on the inv chromosome 9; (maternal, GM01921). ADORA2B:IVS1 and PMP22:IVS3 hybridizations were brighter on the derivative chromosome 17 (paternal, GM06326) and ACR:Ex1-IVS3 hybridizations were brighter on the normal chromosome 22 (maternal, GM10273).