1. CRISPR + CAS = Defensive or Immune System
CRISPR: Clustered Regulatory Interspaced Short Palindromic Repeats
Region of bacterial chromosome containing DNA sequences similar to foreign DNA (spacers) alternating with identical repeated sequences (Figure 10.28)
CRISPR-associated proteins (Cas proteins)
Obtain and store segments of foreign DNA as spacers
Recognize and destroy foreign DNA

2. Figure 10.28 Figure 10.28 Operation of the CRISPR system.
Unique spacer
sequences
Bacterial chromosome
DNA
cas genes
Repeat
Repeat
Cas proteins
Transcription and translation
Transcription
CRISPR RNA
Cutting of RNA by Cas proteins
Foreign sequence is recognized by CRISPR RNA.
Figure Operation of the CRISPR system.
Viral
infection or
conjugation
Viral or plasmid DNA
Cas proteins cut and destroy foreign nucleic acid.
Figure 10.28