The correlation between the hydrophobicity of a mitochondrial transcript and its pyrimidine content. GRAVY scores were calculated using the ExPASy ProtParam website. Linear fit P-values were less than 0.001 for all panels. Linear fit R-values were (A) 0.82 (B) 0.75 (C) 0.90, and (D) 0.88. The numbers of membrane, soluble, and unknown protein-coding genes for the species in panels A-C are found in Table 1.