Should You Choose Your Baby’s Eye Color?

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? You can find transcripts (posted midday) and more information for all episodes at nytimes.com/sway, and you can find Kara on Twitter @karaswisher.