Structure of typical cassettes encoding typical expressed canonical gRNA genes aligned at the 5′ end of the 18 bp forward repeat (position 0 on x-axis). Histograms show the distributions of the positions of expressed canonical gRNA gene components relative to the 5′ end of the forward repeat: Blue: 5′ ends of 5 nt initiation sequences; magenta: 5′ ends of anchors; light green: 5′ ends of guiding regions; dark green: 3′ ends of guiding regions which typically ends 2 nt short of the gRNA gene; orange: 3′ ends of gRNA genes which are typically 49 nt long and commonly end with a T nucleotide; and dark gray: 3′ ends of 18 bp reverse repeats. The colored bars represent the positions of the gRNA gene components based on their median positions within cassettes. The double-headed arrows indicate median distances between cassette features.
