1. A method of inducing reaction between first and second reactive units during a nucleic acid-templated chemical reaction, the method comprising the steps of: (a) providing (i) a template comprising a first reactive unit associated with a first oligonucleotide comprising a codon and (ii) a transfer unit comprising a second reactive unit associated with a second oligonucleotide comprising an anti-codon capable of annealing to said codon, wherein said codon or said anti-codon comprise first and second spaced apart regions; (b) annealing said oligonucleotides together thereby to bring said first reactive unit and said second reaction unit into reactive proximity, wherein said codon or said anti-codon having said first and second spaced apart regions produce a loop of oligonucleotides not annealed to the corresponding anti-codon or codon; and (c) inducing a covalent bond-forming reaction between said reactive units to produce a reaction product.