A new technique to correct mutations that cause disease has shown promise in a human embryo study. The disease β-thalassemia, a blood disorder, is caused by a mistake in a single DNA base. A study in Protein & Cell describes how researchers used what’s known as the base-pair editor system to replace a mutant DNA base with the correct one. Although it only worked 20% of the time, base editing, also known as chemical surgery, could present a “significant technical advance,” The Guardian reports. Unlike CRISPR, the revolutionary genome editor that has received intense attention over the past 5 years, base editing does not require cutting both strands of the DNA to make a repair, theoretically reducing the likelihood of introducing errors.