... Dr. Michael Hansen, a Senior Scientist at Consumers Union, the policy arm of Consumer Reports, wrote, “While genome editing has been portrayed in the media as an incredibly precise process, where one can go in and literally only intentionally change one or a small number of nucleotide bases, the reality is that there can be large numbers of off-target effects.” He says, “This study raises troubling concerns.”

Another recently published study in Nature Communications used CRISPR/Cas9 to make 17 edits in the mouse genome. They too sequenced the genome and found unexpected insertions and deletions in all 17 places. Whereas deletions of approximately 9 base pairs are predicted, the actual size of the deletions was as high as 600 base pairs. No computer model predicts DNA damage this extensive.

A third study published this year also found deletions of more than 500 base units. The researchers also confirmed that proteins produced by these mutated sections were altered. Such changes could theoretically transform a beneficial protein to a harmful one. ...