By gene editing mouse sperm cells first, and then using corrected sperm to make embryos, Li’s mice came out perfect every time.
Yet some scientists agree that sperm may be the most practical avenue for making designer people. “It could turn out to be a very good option,” says George Church, a professor at Harvard University and one of the inventors of the CRISPR technology.
“There is no reason to think it can’t be done,” says George Daley, a noted stem cell researcher at Harvard University’s medical school. From what he’s seen, he says, the prospect of installing custom DNA edits into lab-grown reproductive cells is “very real.”