There is no overwhelming functional imperative for life to be based on DNA or RNA,' says Phil Holliger from the MRC Laboratory of Molecular Biology in Cambridge, UK, who led the team. 'Other polymers can perform these functions, at least at a basic level.' Holliger's team's xeno-nucleic acid (XNA) polymers each replace DNA's ribofuranose sugar ring with six other cyclic structures that can still form helical chains and base pairings. But rather than using relatively inefficient chemical synthesis, the scientists wanted to exploit polymerase and reverse transcriptase enzymes to copy genetic information from DNA templates to XNAs. In living organisms, polymerases can make RNA from nucleotide monomers using existing DNA strands as templates. Reverse transcriptases can then create a copy of the original DNA strand from that RNA in the same way.