Complex amplification of EGFR and PPARGC1A loci. (a) The region within the curly bracket is the tandemly duplicated unit in reverse orientation. It contains a 639 kb region (chr7: 54,973,500-55,632,000, red arrow, carrying the EGFR gene) and its inverted partial duplicate that contains the 1.3 Mb region on chr4 (chr4: 22,864,000-24-249,500, white box, carrying the PPARGC1A gene) and shorter regions from chromosomes 1, 21 and 3 (green, blue and purple boxes). (b) A431 cells in the metaphase, pink probes target amplified EGFR (340 kb), green probes target the centromere of chromosome 7. EGFR is located in chromosome 7 as well as in two minute chromosomes. (c) The probes targeting the PPARGC1A locus (chr4p15) and EGFR are visualized together, confirming the co-localization of these two heavily amplified loci in the minute chromosomes.