Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) are the hallmark of a bacterial defense system that forms the basis for CRISPR/Cas sequence-specific gene targeting technology [1-5].
CRISPR/Cas systems typically consists of two components:
Figure 1: Cas endonuclease and sequence-specific guide RNA (gRNA) can be delivered as ribonucleoprotein (RNP) complex consisting of synthetic gRNA and recombinant Cas endonuclease (A), synthetic gRNA and Cas endonuclease-encoding mRNA (B) or Cas protein and gRNA-encoding expression plasmids (C).
 Jinek et al. (2012) A programmable dual-RNA-guided, DNA endonuclease in adaptive bacterial immunity. Science 337(6096):816.
 Wang et al. (2016) CRISPR/Cas9 in Genome Editing and Beyond. Annu. Rev. Biochem. 85:227.
 Gaj et al. (2013) ZFN, TALEN, and CRISPR/Cas-based methods for genome engineering. Trends Biotechnol 31(7):397.
 Aldi et al. (2018) The CRISPR tool kit for genome editing and beyond. Nature Communications 9:1911.
 Pickar-Oliver et al. (2018) The next generation of CRISPR–Cas technologies and applications. Nature Reviews Molecular Cell Biology 20:507.
 DeWitt et al. (2017) Genome editing via delivery of Cas9 ribonucleoprotein. Methods 121:9.
 Kim et al. (2014) Highly efficient RNA-guided genome editing in humancells via delivery of purified Cas9 ribonucleoproteins. Genome Research 24:1012.