Neighboring bases are not independet P air Observed/Expected Example TG 1.29 CT 126 Dinucleotide frequencies CC in some vertebrate AG 1.16 Squences AA 15 CA 1.15 GG 1.14 Based on 166 vertebrate TT 1.07 sequences, totaling GA 1.0 136, 731 bases(Nussinov, TC 1.00 1984) GO 0.99 AT 0.85 AC 0.84 GT 0.82 Pn≠PuPv TA 0.65 CG 0.42Neighboring bases are not independet Pair Observed/Expected TG CT CC AG AA CA GG TT GA TC GC AT AC GT TA CG 1.29 1.26 1.18 1.16 1.15 1.15 1.14 1.07 1.04 1.00 0.99 0.85 0.84 0.82 0.65 0.42 Example: Dinucleotide frequencies in some vertebrate squences. Based on 166 vertebrate sequences, totaling 136,731 bases (Nussinov, 1984) Puv ≠ PuPv