Figure 2 in Agricultural Research Service Weed Science Research: Past, Present, and Future

Figure 2. (A) Depiction of a bipartite synthetic Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) cassette (red) consisting of a Cas9 endonuclease and a guide ribonucleic acid RNA (gRNA) that is flanked by homology arms (HA) (black). (B) Following expression of the CRISPR cassette, gRNA binds to Cas9 and directs the complex to a unique sequence-specific site for DNA cleavage and homology-directed repair (HDR). Following HDR, the CRISPR cassette is copied into both genomic regions. (C) Standard Mendelian inheritance results in 50% of progeny inheriting a modified gene. In contrast, a gene drive would bias inheritance, theoretically resulting in all progenies (~99%) inheriting the modified gene, thereby "driving" the modified gene into an invasive weed population.