Professor Graham Cook's suggestion1 that serine in the primordial soup played a role in determining the left-handedness of amino acids in organisms is complemented by the possibility that this amino acid played a critical role in initiating evolution of the genetic code.2 Serine-containing peptides form hydrogen bonds to the nucleotide base cytosine, as shown in the accompanying formulation. The presence of serine codons largely in the cytosine column of the present code may then imply a derivation of the present code from the original.
Simon Black
Scientist Emeritus
National Institutes of Health
Bethesda, Md.
SimonB@bdg8.niddk.nih.gov
