Scientists are closing in on techniques that could let them safely repair almost any defective gene in a patient, opening the door for the first time to treatments for a range of genetic disorders that are now considered incurable.

The breakthrough relies on “zinc fingers” (amino acid protuberances that emanate from a zinc ion). When inserted into human cells, the fingers automatically bind to miscoded strands of DNA, spurring the body’s innate repair mechanism to recode the problem area with the correct gene sequence.