But in the CRISPR system, the guide was not a protein but a snippet of RNA. This had a big advantage. With ZFNs and TALENs, you had to construct a new protein guide every time you wanted to target a different genetic sequence to cut; it was difficult and time consuming. But with CRISPR you merely had to fiddle with the genetic sequence of the RNA guide. A good student could do it quickly in a lab.
