The sequence in one strand of target DNA identical to the gRNA is called the protospacer
A particular motif is required for Cas9/gRNA recognizing & cleavage in the 3'-end out of the protospacer, which is usually -NGG
, named as PAM
(protospacer adjacent motif).
Some reports suggest the PAM type, and the mismatch numbers in different regions (seed
region) of protospacer, show different effects on the efficiency of Cas9/gRNA. In brief, the off-target effects of Cas9/gRNA is under discovery.
(a review of human cell)