Compositional nonrandomness: a quantitatively conserved evolutionary invariant.
The a priori probability that the amino acid composition of a protein will exhibit a given overall deviation from the genetic code table frequencies is the same for all protein families independent of protein length, biological function, or origin.
D000595:Amino Acid Sequence; D005075:Biological Evolution; D005815:Genetic Code; D008954:Models, Biological; D011336:Probability