Genome editing enables scientists to alter the DNA sequence of cells. This technology has great potential for research and therapeutic applications. One challenge, however, is that editing often works only in a small fraction of cells. Researchers must therefore find ways to separate the successfully edited cells from all the others. In a new study, scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig present a new efficient strategy for selection, that uses programmable gene scissors to selectively kill unwanted cells. The team also demonstrates that this method can be used to precisely kill cells with cancer mutations in the lab.