According to the Scripps Research scientists, this finding is a significant step towards expanding the genetic code and the ability of DNA to act as an information storage and retrieval system in the test tube and in simple, engineered organisms, such as yeast or bacteria. DNA with three or more base pairs could find broad applications in a number of fields, including biotechnology, medicine, data storage, and security.
Instead of just the canonical base pairs "G-C" or guaninecytosine, and "A-T" or adeninethymine, the Scripps Research scientists' DNA has a third pairing: "3FB-3FB" between two unnatural bases called 3-fluorobenzene (or 3FB). Unlike other unnatural base pairs, DNA polymerases are able to replicate this base pair, albeit with reduced fidelity. To improve replication, the scientists also reported the development of a system capable of evolving polymerases to better recognize 3FB in DNA. Using a selection system some liken to evolution in the test tube, they are creating their own "polymerase" enzyme able to replicate the unnatural DNA.
While the polymerase does not replicate the unnatural DNA with the same fidelity observed in nature, (roughly one mistake for every 10 million bases of DNA copied), its fidelity is reasonable (typically making only one mistake for every1000 base pairs). This is the first time anyone has been able to replicate unnatural DNA with fidelity against every possible mispair.
"We definitely are still working on improvements, especially in fidelity," says Scripps Research Assistant Professor Floyd Romesberg, who led the research. "Nevertheless, we are now able to replicate unnatural DNA."