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. Author manuscript; available in PMC: 2011 Jul 10.
Published in final edited form as: Cell. 2009 Feb 20;136(4):615–628. doi: 10.1016/j.cell.2009.01.043

Figure 3. Gene Arrangement and Regulatory Functions of CRISPR RNAs.

Figure 3

CRISPR arrays are comprised of DNA repeats (black triangles) separated by unique spacers (red hatched boxes). CAS genes (blue) which encode proteins that function in CRISPR RNA processing and/or DNA silencing are located nearby. The CRISPR arrays are initially transcribed as a long RNA, which is subsequently processed by the Cascade complex (blue circles and ovals) to individual repeat-spacer units, called crRNAs. These crRNAs target foreign DNA through an unknown mechanism likely involving other CAS proteins and the degradation of the exogenous DNA.