The prospect of artificial life has just come one step closer, with the discovery that a synthetic version of DNA and RNA can evolve like the real thing.
While DNA is built using deoxyribose sugars and RNA with ribose, an international team has now discovered it's possible to replace these sugars with six others to create synthetic genetic chains called xeno-nucleic acids (XNAs).
The XNAs can share information with DNA - and one, anhydrohexitol nucleic acid,or HNA, can undergo directed evolution and fold into biologically useful forms.
The work sheds new light on questions concerning the origins of life.
Both RNA and DNA embed data in their sequences of four nucleotides, coding for hereditary traits and the recipe for building proteins from amino acids.
According to one hypothesis, RNA, which is simpler, preceded DNA as the basis of life. However, the spontaneous appearance of RNA through random mixing of primitive chemicals is unlikely to have occurred without some sort of intermediate stage.
"This is a big question," says John Chaput of Arizona State University.
"If the RNA world existed, how did it come into existence? Was it spontaneously produced, or was it the product of something that was even simpler than RNA?"
Threose nucleic acid (TNA) is one candidate, having the ability to bind with RNA through antiparallel Watson-Crick base pairing.
"This property provides a model for how XNAs could have transferred information from the pre-RNA world to the RNA world," says Chaput.
"Further down the road, through research like this, I think we'll have enough information to begin to put the pieces of the puzzle together."