(NPR) – First, it was human embryos. Now scientists are trying to develop another way to modify human DNA that can be passed on to future generations, NPR has learned. Reproductive biologists at Weill Cornell Medicine in New York City are attempting to use the powerful gene-editing technique called CRISPR to alter genes in human sperm. NPR got exclusive access to watch the controversial experiments underway. The research is aimed at finding new ways to prevent disorders caused by genetic mutations that are passed down from men — including some forms of male infertility.

The team is starting with a gene that can increase the risk for breast, ovarian, prostate and other cancers. The experiments are just starting and have not yet been successful. But the research raises many of the same hopes — and fears — as editing the DNA of human embryos. Nevertheless, the researchers defend the work. “I think it’s important from the scientific point of view to investigate in an ethical manner to be able to learn if it’s possible,” says Gianpiero Palermo, a professor of embryology in obstetrics and gynecology at Weill Cornell Medicine, who runs the lab where the work is being conducted. CONTINUE