CRISPR-Cas9 is the kind of scientific breakthrough that could change human evolution. Scientists call it “genetic scissors” — a tool that snips DNA with powerful and scary precision. As Dr. Jennifer Doudna, the co-developer of the gene-editing technology, explains, scientists can now edit the genomes of living organisms “like you might edit a Word document.”

Dr. Doudna and her collaborator, Dr. Emmanuelle Charpentier, won the Nobel Prize in Chemistry this year. Their pioneering research could pave the way for a cure for cancer. Some fear it could be used to create designer babies.

So what does this technology mean for how we live — and die? How will potential profit complicate the incentives of scientists? And just because we can more precisely “edit” life, should we?

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