Figure 2: Overview of the CRISPR-Cas9 system: The CRISPR/Cas9 system that can target a specific gene sequence Step 1A) Acquisition of target sequence: insertion of new foreign DNA sequence (called spacer) into the CRISPR locus. Step 2B) Expression: transcription of the CRISPR locus and processing of CRISPR RNA. Step 3C) Silencing/Degradation: detection and degradation of mobile genetic elements by CRISPR RNA and Cas protein(s).