PAM gene copy numbers, mRNA expression and C-terminal amidation for clones transfected using ZFN pDNA. The PAM gene copy numbers (a), PAM mRNA expression levels (b; calculated per ACTB housekeeping gene), and prolinamide content on the recombinant mAb (c) for the three best ZFN knock-out clones derived from the CHO Der2 and CHO Der3 parental cell lines, where ZFN pDNA was used for the transfection. Prolinamide was reduced to 6%. The copy numbers and mRNA expression levels were determined using qPCR, and the data are means ± standard deviations of two technical replicates. The prolinamide content was determined using CEX, and these data are means ± standard deviations of two biological replicates.