Unnatural base pair systems for DNA/RNA-based biotechnology

The development of unnatural, extra base pairs could expand genetic information, by enabling the site-specific incorporation of functional components into nucleic acids and proteins. Researchers have been trying to create unnatural base pairs by drawing upon non-standard hydrogen-bonding topologies, shape complementarity, and/or hydrophobic interfaces, to confer sufficient selectivity and efficiency to work with the natural A–T(U) and G–C base pairs in replication, transcription and translation. The development of artificial genetic systems has been broadly advanced by combining the extra base pairs with modified natural components, including the base pairs, substrates and polymerase enzymes.