The higher the amount of fluorescence, the better that gRNA is at causing a double stranded
break at the target site, allowing the two halves of EGFP to recombine by homology directed repair, and resulting in the expression of EGFP.
For editing the genome, this system makes use of 3 components, a guide RNA (gRNA) of about 125 nt that specifies the
target, the Cas9 endonuclease that creates the DNA double - strand
break (DSB)
at the
target site, and a donor oligonucleotide or plasmid as the repair material if needed (for knock in models).