Figure 2.

Expected and observed guanine compositions. The nucleotide composition was examined in four scenarios: total frequencies (A to C), frequencies at first (D to F), second (G to I), and third (J to L) codon positions. The expected and observed guanine compositions were quantitated in Archaea (A, D, G and J), Bacteria (B, E, H and K), and Eukarya (C, F, I and L). Each point in all plots represents a sum of the composition from the species coding sequences and similar plots for all other nucleotides were summarized in Additional file 2.