Gene-Drive Versus Allelic Drive (IMAGE) University of California - San Diego Caption Gene-drive is mediated by a guide RNA (gRNA) that cuts at the exact site (scissors) where the gene-drive element (blue box: Cas9 gene; yellow box: gRNA) is inserted into the genome, resulting in full gene-drive element copying. Right panel: The new allelic drive is accomplished by the addition of a second gRNA (blue box) to a gene drive element that preferentially cuts a detrimental allele (scissors), but not the beneficial allele, resulting in beneficial allele copying. Credit Bier Lab, UC San Diego Usage Restrictions Must be used in conjunction with allelic drive paper. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.