The local alignment scoring matrix used when aligning a nucleotide sequence against its reverse complement. Matches score 5 points, while mismatches are penalized by 4. All unresolved ambiguous loci are treated as an N regardless of which bases are more probable. This matrix appears to work best at predicting the secondary structures of the known 190 pre-miRNA. Note that G-A and U-C mismatches are not penalized as much to accommodate the occurrence of G-U and U-G base pairs respectively.