Table 2.

Key characteristics in CRISPR and siRNA technologies.

	siRNA	CRISPR
Targeting sequence	siRNA Oligonucleotide shRNA plasmid	(Synthetic sgRNA) sgRNA plasmid
Effector	- (Endogenous)	Cas9 Endonuclease
Effect	Knockdown (variable)	Knockout (Silencing, Activation)
Time to effect	2–3 days	Days; may require selection
Libraries	Lentiviral shRNA Pools Lentiviral shRNA arrays Arrayed siRNA Sub-panels	Lentiviral sgRNA Pools
Off-target effects	High	No consensus reached – Depending on policy of lab off-targets may be absent or very high

For an overview of key differences between siRNA and CRISPR technologies, please see Taylor and Woodcock (2015).