Cas9 protein

In this figure, “A” shows where the Cas9 protein (blue) binds to a sgRNA to guide it to a specific DNA sequence. “B” shows the wild-type Cas9 normally cleaving the DNA at the target sequence. Researchers modified the Cas9 to be unable to cut DNA (now called dCas9), which instead blocks RNA polymerase (RNAP, red) from moving along the DNA, stopping transcription.(Credit: SynBERC)