Quantification of ErbB1 gene copy number in A549 and HK2 cell lines. (A) The presence of centromere 7 (red) and ErbB1 gene (green) was visualized by fluorescence in situ hybridization. The nuclei were visualized by interference contrast (DIC). (B) The copy number of ErbB1 and centromere 7 per nucleus. One hundred cells of each strain were analyzed.