Synthetic DNA and RNA seen to evolve PHOENIX, April 20 (UPI) -- The discovery that synthetic DNA and RNA can evolve like their natural counterparts could bring artificial life one step closer, U.S. scientists say. DNA is built using deoxyribose sugars and RNA with ribose, but scientists have discovered how to replace these sugars with six others to create synthetic genetic chains called xeno-nucleic acids or XNAs. The synthetic XNAs can share information with natural DNA and one, anhydrohexitol nucleic acid, can undergo evolution and become biologically useful forms, they said. The findings could shed new light on questions concerning the origins of life, researchers said. RNA, which is the simpler molecule, is thought to have preceded DNA as the basis of life, scientists say. However, the spontaneous appearance of RNA through random mixing of primitive chemicals is unlikely to have occurred without an intermediate stage, they say -- perhaps something like XNAs. "This is a big question," researcher John Chaput of Arizona State University told TG Daily. 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? One nucleic acid known as threose is a candidate, having the ability to bind with RNA. "This property provides a model for how XNAs could have transferred information from the pre-RNA world to the RNA world," Chaput said.