This index is the frequency of aromatic amino acids (Phe, Tyr, Trp) in the hypothetical translated gene product. The hydropathicity and aromaticity protein scores are indices of amino acid usage. The strongest trend in the variation in the amino acid composition of E. coli genes is correlated with protein hydropathicity, the second trend is correlated with gene expression, while the third is correlated with aromaticity ( Lobry and Gautier 1994). The variation in amino acid composition can have applications for the analysis of codon usage. If total codon usage is analysed, a component of the variation will be due to differences in the amino acid composition of genes.

This definition is in context to Yeast Genome. See more contextual defintions for Aromaticity Score (Aromo).