immune system of bacteria

1. CRISPR Cas
Raffia siddique

2. (Barrangou and Marraffini, 2014)

5. Figure 1. Overview of clustered regularly interspaced short palindromic repeats
(CRISPR)/CRISPR associated (Cas) adaptive immunity. (a) Adaptation. The CRISPR arrays are
composed of short repeats and intervening sequences derived from foreign invaders. Upon
infection with a foreign element (e.g., phages or plasmids), part of the genome is typically
incorporated into the leader end of the CRISPR array and the repeat is duplicated. The
CRISPR arrays are located adjacent to a cluster of cas genes; (b) crRNA generation. The
CRISPRs are transcribed into pre-crRNAs that are then processed into mature crRNAs; (c)
Interference. The crRNA, in a complex with Cas proteins, binds and degrades the target
nucleic acid of the invading element(Richter et al., 2012)

6. References
• BARRANGOU, R. & MARRAFFINI, L. A. 2014.
CRISPR-Cas Systems: Prokaryotes Upgrade to
Adaptive Immunity. Mol Cell, 54, 234-244.
• http://playit.pk/watch?v=9IgLrOEsauk
• http://playit.pk/watch?v=UAppRRKy8go
• RICHTER, C., CHANG, J. T. & FINERAN, P. C. 2012.
Function and regulation of clustered regularly
interspaced short palindromic repeats (CRISPR) /
CRISPR associated (Cas) systems. Viruses, 4, 2291-
311.