Correlation between GC content of genomes and excess of certain off-frame codons calculated using the 2–3 Markov model. The top graph shows the correlation between the GC content and the excess of OSCs in the organisms studied; as predicted by the Ambush Hypothesis this graph has a significantly positive correlation. The graphs in the second row show the correlation between the GC content and the excess with which each stop appears out-of-frame; it should be noted that only TGA shows a positive correlation as predicted by the hypothesis, while TAA and TAG show negative correlations in opposition to the hypothesis’ prediction. The graphs in the third row show the same correlation but for the TGG, TGC and TGT codons; all three of these codons show significant positive correlations, with TGG and TGC showing even stronger and more significant correlations than TGA. The 5–3 Markov model gives similar results (data not shown).