CRISPR-Cas9 is not the first method available to scientists for modifying DNA; it is by far, however, the easiest to use. With CRISPR-Cas9, the crRNA/tracrRNA sequence or an artificial guide RNA ...

Its primary component, the Cas9 enzyme (orange), cuts genomic DNA (blue). The enzyme is directed to its target--essentially any sequence along the genome--by hitching it to a strand of guide RNA ...