Glycol nucleic acid (GNA) is a polymer similar to DNA or RNA but differing in the composition of its "backbone". GNA is not known to occur naturally; they are synthesized chemically. The 2,3-dihydroxypropylnucleoside analogues were first prepared by Ueda et al. (1971). Soon thereafter it was shown that phosphate-linked oligomers of the analogues do in fact exhibit hypochromicity in the presence of RNA and DNA in solution (Seita et al. 1972). The preparation of the polymers was later described by Cook et al. (1995, 1999) and Acevedo and Andrews (1996). The GNA-GNA self-pairing described by Zhang and Meggers is however novel, and the specificity of interaction well-demonstrated.