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CRISPR Causes Unexpected Outcomes Even at the Intended Site of Genetic Modification

Implications for food safety of gene-edited crops have not been investigated

Yet another study has shown that the new GM technique CRISPR resulted in unexpected effects. The findings could have implications for the food safety of gene-edited crops produced using this genetic engineering tool.

In the new study (see abstract below), the authors investigated the outcomes in cells when the CRISPR system was used to knock-out a gene function by disrupting its normal base unit sequence. This disruption takes the form of DNA base unit insertions and deletions ("indels"). Indels are produced by the DNA repair process known as non-homologous end joining (NHEJ), which gets activated in order to repair the cut ends of the DNA molecule once the CRISPR has made its double-strand DNA break.

The authors found that instead of the intended outcome of totally destroying the function of a CRISPR-targeted gene, in 50% of the cell lines investigated, the indels resulted in an alteration of the gene’s DNA base unit sequence, so that it now produced new types of mRNAs (messenger RNA molecules) or proteins.