The proportion of selectable siRNAs and mRNAs according to Tm values in the seed-target duplexes. (A) The percentage of selectable siRNA candidates for human mRNAs according to the Tm values in the seed-target duplexes. The total number of siRNA (56,375,087) is set to 100%. (B) The percentage of human mRNAs harboring at least one target sequence of an siRNA whose Tm value of the seed-target duplex is below the indicated value. 100% indicates 25,651 mRNAs. Off-target hits with 0-4 mismatches between nucleotides at positions in the 2-20 of both siRNA strands and human mRNAs were represented as separate lines.