English: Transcripts of the CRISPR Genetic Locus and Maturation of pre-crRNA 1. The CRISPR locus of S. pyogenes consists of a cas operon, a CRISPR array, and genes coding for trans-activating crRNA (tracrRNA). tracrRNA, Cas9 RNA and pre-crRNA are transcribed from the CRISPR genetic locus. tracrRNA then forms a tertiary structure with three loops and Cas9 RNA is further translated in protein. 2. Because pre-crRNA is synthesized as a continuous stretch, a maturation process follows. In this process, tracrRNAs pair with repeat sequences of pre-crRNA. Cas9 protein is recruited to form a ternary complex with the tracrRNA and pre-crRNA. Single complexes are then released through cleavage by RNAse III enzymes. 3. The surveillance and interference complex consists of Cas9 and a duplex of tracrRNA and crRNA. crRNA contains the spacer sequence for comparison with DNA, and a sequence to form a duplex with tracrRNA.