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Table 1 Mathematical analysis of the sgRNA off-target homologies

From: Whole genome analysis of CRISPR Cas9 sgRNA off-target homologies via an efficient computational algorithm

Total combination of 20 bp 1,099,511,627,776
Mismatches in seed sequence Number of combinations
0 1
1 36
2 594
Mismatches in non-seed sequence Number of combinations
0 1
1 24
2 252
3 1512
4 5670
Total base mismatches 236,401
DNA bulge with 0 base mismatch 64
RNA bulge with 0 base mismatch 60
DNA bulge with 1 base mismatch 2112
RNA bulge with 1 base mismatch 1968
RNA bulge of two bases 32
Total combinations of homologies 240,637
Off-target homology probability of a 20-base DNA sequence 0.00000021886
Probability of potential PAM 0.2500
Off-target homology probability 0.00000005471