Editing Human Embryos: So This Happened

Earlier this week, Chinese researchers reported that they edited the genes of human embryos using a new technique called CRISPR. While these embryos will not being growing up into genetically modified people, I suspect this week will go down as a pivotal moment in the history of medicine. David Cyranoski and Sara Reardon broke the news today at Nature News. Here I’ve put together a quick guide to the history behind this research, what the Chinese scientists did, and what it may signify.

There are thousands of genetic disorders that can occur if a mutation happens to strike an important piece of DNA. Hemophilia, sickle cell anemia, cystic fibrosis– the list goes on and on. As I wrote in the Atlantic in 2013, a particularly cruel genetic disorder, fibrodysplasia ossificans progressiva causes people to grow a second skeleton. It’s caused by a mutation that changes a single “letter” of a single gene, called ACVR1. The protein encoded by the gene doesn’t work properly, triggering a wave of changes in people’s bodies, with the result that when they heal from a bruise, they replace...