Within individual yeast genes, codons with higher demands for translational accuracy have slower elongations. A total of 1,843 genes are used.

<p>(A) Cumulative frequency distributions for the observed and randomly expected within-gene rank correlations between the evolutionary conservation of the encoded amino acid of a codon and its elongation speed. KS test, Kolmogorov–Smirnov test of the equality of the two distributions. Only 1,590 genes are used here because correlation cannot be calculated for the other 254 genes due to the lack of variation (or having too few sites with necessary data) in either evolutionary conservation or elongation speed. (B) Cumulative frequency distributions for the observed and randomly expected odds ratio <i>OR</i>₁, which measures the enrichment of slow-elongation codons at evolutionary conserved residues within a gene. (C) Combined <i>OR</i>₁ for all genes examined, by the MH procedure. The combined <i>OR</i>₁ significantly exceeds 1 (<i>p</i><10⁻⁷, MH test). Error bar indicates one standard error, estimated by bootstrapping the genes 1,000 times.