Can we change the DNA in sperm? DR TONY BRAIN/SCIENCE PHOTO LIBRARY

For the first time, biologists are trying to get the CRISPR gene-editing machinery directly into mature human sperm, rather than into fertilised embryos. The work is still at an early stage but could lead to a new way to prevent inherited diseases.

Around half a dozen teams have used the CRISPR genome-editing method to alter the DNA of human embryos but it is still far from clear whether this approach is safe. One issue is that the embryo can start dividing before its DNA is corrected, meaning …