One concern is the fact that the technique is still fairly innacurate, and results in a lot of accidental mutations in other parts of the genome. (businessinsider.com)
But even though CRISPR can precisely target specific stretches of DNA, it sometimes hits other parts of the genome. (sciencedaily.com)
North and her co-workers found that the region surrounding the mutant version of the gene showed less variability than did other parts of the genome, a sign of positive natural selection. (sciencemag.org)