Table 1.

Most Eukaryotic Species Show a Tendency Toward Weak 5′-mRNA Structure and High 5′-Codon Bias in Shorter Genes

Correlations with ORF Length	5′ Free Energy (120 Species)	5′-CAI (89 Species)
% Species with negative correlation	82	83
% Species with significant negative correlation	73	67
% Species with positive correlation	18	17
% Species with significant positive correlation	11	15
Two-sided binomial P value	1.2 × 10−12	1.5 × 10−10

Note.—In particular, there is a negative rank correlation between 5′-mRNA folding energy and ORF length in 82% of the 120 eukaryotic species tested, and similarly, a negative rank correlation between 5′-CAI and -ORF length in 83% of the 89 species tested. The overall tendency toward negative correlations is highly significant, in both cases.