In two studies, one in Nature and another in Science, researchers from the Broad Institute of MIT and Harvard describe a new way to edit DNA and RNA, called base editing. The approach could one day treat a range of inherited diseases, some of which currently have no treatment options. In the Nature study, researchers led by David Liu, a Harvard chemistry professor and member of the Broad Institute, were able to change an A into a G. Such a change would address about half the 32,000 known point mutations that cause disease. To do it, they modified CRISPR so that it would target just a single base. The editing tool was able to rearrange the atoms in an A so that it instead resembled a G, tricking cells into fixing the other DNA strand to complete the switch. As a result, an A-T base pair became a G-C one. The technique essentially rewrites errors in the genetic code instead of cutting and replacing whole chunks of DNA. Substitutions of a G for an A in certain parts of the DNA represent about 15 percent of disease-associated point mutations. In the new Science study, Feng Zhang, of the Broad Institute and MIT, used a similar base-editing method to target individual letters in RNA, DNA’s chemical cousin. RNA naturally degrades in the body, so editing RNA wouldn’t result in a permanent change to a person’s genome.