In prebiotic chemistry on Earth billions of years ago, zinc most likely was the first effective nonenzymatic polymerase. Zinc remains an essential component of all DNA and RNA polymerases examined today. With a poly C template, Zn2+ ions alone can catalyze the assembly of an activated GMP derivative (guanosine 5'-phosphoimidazolide) into poly G chains 30 to 40 residues in the natural 3'-5' linkage. Although other metals are catalytic, Zn2+ ions produces the greatest fidelity.1
Zinc's function as a nonenzymatic polymerase suggests an inorganic answer to the age-old question, "Which came first the chicken or the egg?"
1 Kornberg A., Origin of DNA on Earth. In:1982 Supplement to DNA Replication. San Francisco:W.H.Freeman Co.;1982:S224.