J. Mol. Evol. 11,199--210 (1978) Journal of Molecular Evolution O by Springer-Verlag 1978 Genetic Code Correlations: Amino Acids and Their Anticodon Nucleotides A.L. Weber* and J.C. Lacey, Jr. Laboratory of Molecular Biology, University of Alabama in Birmingham, Birmingham, A1 35294, USA Summary. The data here show direct correlations between both the hydro- phobicity and the hydrophilicity of the homocodonic amino acids and their anticodon nucleotides. While the differences between properties of uracil and cytosine derivatives are small, further data show that uracil has an affinity for charged species. Although these data suggest that molecular relationships be- tween amino acids and anticodons were responsible for the origin of the code, it is not clear what the mechanism of the origin might have been. Introduction Our research has, for a number of years, been based on the belief that there is a defi- nite and measurable physico-chemical basis for the origin of the genetic code. This work has included studies of molecular complexes of mononucleotides with polylysine (Lacey and Pruitt, 1969), complexes of thermal proteinoids with polynulceotides (Fox et al., 1971) and investigations of activated forms of amino acids (Lacey and White, 1972; Weber and Fox, 1973; White et al., 1973; Weber and Lacey, 1974; Weber and Lacey, 1975). These latter studies were based on a further belief that one must understand the molecular basis for the origin of protein synthesis (i.e. the chemical reactions involved), as well as specificities for coding (Lacey et al., 1975). We recently reviewed our work, including some of the present data, and discussed possible mech- anisms for the coordinate evolution of the code and the process of protein biosyn- thesis (Lacey and Weber, 1977). Woese et al. (1966) gathered information on the hydrophobicities of amino acids, and were the first to suggest that hydrophobic-hydrophilic properties of amino acids and nucleotides were important in a consideration of the origin of the code. More recently, Fendler et al. (1975), and Nagyvary and Fendler (1974), carried out work on the affinity of amino acids and nucleotides for micelles. From their data one can infer a general anticodonic relationship of properties of amino acids and nucleotides. *Present Address: The Salk Institute, P.O. Box 7809, San Diego, CA 92112, USA 0022--2844/78/0011/0199/4 2.40