The standard gene-editing tool, CRISPR-Cas9, frequently produces a type of DNA mutation that ordinary genetic analysis misses, claims new research published in the journal Proceedings of the National Academy of Sciences (PNAS). In describing these findings the researchers called such oversights “serious pitfalls” of gene editing (Skryabin et al., 2020). In all, the new results suggest that gene-editing is more error-prone than thought and, further, that identifying and discarding defective and unwanted outcomes is not as easy as generally supposed.
Derived originally from the bacterium streptococcus pyogenes, CRISPR-Cas9 is a DNA cutting and targeting system. CRISPR stands for clustered regularly interspaced short palindromic repeats and refers to the RNA molecule that is the targeting component of the system. This CRISPR RNA is sometimes also referred to as the guide RNA. The Cas9 component is a nuclease, that is, an enzyme that cuts DNA. Thus, in the editing process, the Cas9 enzyme is guided to the intended cut site by the CRISPR RNA. The whole assembly is often just called CRISPR.