A) Solid phase transfection of nontargeting (scrambled) or PLK1 targeting gRNAs into Cas9 expressing RPE-1TP53 -/- cells. Cells were fixed after 24, 48 and 72 hours and imaged after DNA staining with Hoechst. Green arrowheads indicate examples of prometaphase arrested cells, and the red arrowheads indicate examples of dead cells due to Plk1 downregulation. Phenotypic penetrance is indicated at the top of each panel with standard deviation derived from 2 independent experiments. Scale bar, 20 μm. 