Frequency of defined trinucleotides of decoy 3′ splice sites in candidate In100 elements (numbers observed and expected for introns/exons)

χ2 = 196.3 for df = 3 indicates a probability that is very low (P = 4.2×10−42), thus there is a significant excess (∼20%) of the In100 element candidate as defined by CAG at the last three positions of the decoy 3′ splice site inside the In100-like elements located in introns. The opposite pattern is observed for CAG inside the In100-like elements located in exons: depletion of 11% (X2 = 9.7 for df = 3; P = 0.021). The expected numbers were calculated separately by the nucleotide composition of intronic regions: 0.28 for A, 0.31 for T, 0.20 for C and 0.21 for G; and of exonic regions: 0.258 for A, 0.246 for T, 0.246 for C and 0.25 for G [43].