Finding new ways to spell L-I-F-E

XNA molecules join DNA and RNA in the genetic catalog

2012 SCIENCE NEWS TOP 25: 11

Life’s menagerie of hereditary molecules got a little bigger this year. By replacing the sugars in the backbone of a DNA strand with other molecules, scientists created ANA, TNA, HNA, FANA, CeNA and LNA (SN: 5/19/12, p. 10). Each of these synthetic genetic molecules, collectively known as XNAs (xenonucleic acids), also got its own designer enzymes that allow the molecule to be “read” and then replicated, an advance that could help shed light on how life on Earth got its start.


XNAs can make new generations of themselves, though they need an assist from good old DNA. By selecting for a particular trait, such as the ability to attach to another molecule, researchers also coaxed the XNAs to change over time. That covers two biggies: heredity and evolution, now demonstrated to be the purview of not just DNA and RNA.

The work suggests that life, on the early Earth or somewhere else in the universe, could have emerged from other breeds of molecules.

There are also potential biomedical applications: Because researchers can direct the molecules’ evolution, designer XNAs could be made with specialized traits for delivering drugs. The newcomers might also provide replication machinery for new organisms constructed from scratch.

“We only know this one example of life — it’s what’s been on Earth for 4 billion years,” says biochemist Gerald Joyce of the Scripps Research Institute in La Jolla, Calif. “Maybe we’ll find evidence of some kind of life on Europa [a moon of Jupiter] or fossilized life on Mars. Or maybe we’ll just make it.”

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