Table 2.

Most Species Exhibit a Tendency Toward Weak 5′ Free Energy in Short Genes, Even After Controlling for 5′-CAI

Correlation between ORF Length and Quantile of Observed 5′ Free Energy	% Species (of 120 Tested)
Negative correlation	84
Significant negative correlation	65
Positive correlation	16
Significant positive correlation	2.5
One-sided binomial P value	5.38 × 10−15

Note.—In the majority of species tested, we find a negative rank correlation between ORF length and the quantile of the observed 5′-mRNA free energy among the free energies of permuted sequences that retain the same 5′-CAI value. The tendency toward negative correlations across species is highly significant.