The oligomerization of activated D- and L- and racemic guanosine-5'-phosphoro-2-methylimidazole on short templates contg. D- and L-deoxycytidylate has been studied. Results obtained with D-oligo(dC)s as templates are similar to those previously reported for expts. with a poly(C) template. When one L-dC or two consecutive L-dCs are introduced into a D-template, regiospecific synthesis of 3'-5' oligo(G)s proceeds to the end of the template, but three consecutive L-dCs block synthesis. Alternating D-,L-oligomers do not facilitate oligomerization of the D-, L-, and racemic 2-guanosine-5'-phosphoro-2-methylimidazole. We suggest that once a "predominately D-metab." existed, occasional L-residues in a temp. would not have led to the termination of self-replication. [on SciFinder (R)]