Infographic: Two Guide RNAs Make for Large, Stable Insertions

A new technique goes beyond CRISPR and writes two complementary strands of DNA directly into the genome.

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Dan Robitzski

Dan is a Staff Writer and Editor at The Scientist. He typically works on the news desk and joined the team in 2021. He has a background in neuroscience and earned his master's in science journalism at New York University.

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Jun 13, 2022

Two prime editing guide RNAs (pegRNAs), deliver Cas9 enzymes to targeted regions of the genome. The enzymes nick opposite strands of the DNA at different points, at which point the pegRNA serves as a template for the desired gene insertion. This results in two single-stranded DNAs (ssDNA) that bind to each other due to their partially complementary sequence and, if they outcompete the original DNA, are integrated into the genome and completed by the host cell’s existing DNA repair machinery. Because two pegRNAs are used, GRAND editing can insert segments of up to 1,000 base pairs long—more than what one pegRNA could deliver alone.

Two prime editing guide RNAs (pegRNAs), deliver Cas9 enzymes to targeted regions of the genome.
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This article was featured in June 2022, Issue 2 of the digest