Guanine quadruplexes folding in single-strand DNA have been extensively studied for some time. But far less attention has been paid to systems arising in duplex DNA or RNA. Furthermore, the literature shows an apparent absence of quadruplex systems generated exclusively by other nucleic acid bases. With guanine quadruplexes (G4s) as a benchmark, a comparison is made here with equivalent complexes folding in DNA and RNA when derived from cytosine, thymine and adenine. Molecular dynamics simulations determined cytosine and thymine models in DNA as relatively fragile systems, but all non-guanine RNA models were found to be stable into biologically relevant times. Uniquely biplanar or triplanar adenine quadruplexes (A4s) have ostensibly not been described. Adenine models constructed for this work were resolved in silico with stabilities comparable to known guanine equivalents. These complexes achieved further significance with the advent of SARS-CoV-2.RNA viruses are characterised by a poly-adenylated structure capping the genomic terminus. This poly(A) tail is crucial to a cascade of viral replicative activity occurring both extra- and intra-cellular during infection. As a route to proposing potential chemotherapy, this study suggests simple biplanar A4s may fold in this poly-adenylated domain. Notably, mRNA configured as a biplanar A4, shows less dynamic activity than DNA equivalents. This observation may be especially relevant in a physiological context. In contrast to well-characterised guanine quadruplexes, co-ordination with cations appears not to impact on stability. These conclusions may apply to SARS-CoV-2, its variants and other pathogenic RNA viruses.The thesis also infers models of potential interactions between small nucleolar RNAs and long non-coding RNAs may have biological relevance. Non-canonical base-pairing in some instances suggests a molecular mechanism for dysfunction in the development of the embryonic pre-frontal cortex.