Synthetic Genetic Evolution

By RUTH WILLIAMS - THESCIENTIST
Added: Mon, 23 Apr 2012 01:37:24 UTC

Scientists show that manmade nucleic acids can replicate and evolve, ushering in a new era in synthetic biology.

Synthetic genetic polymers, broadly referred to as XNAs, can replicate and evolve just like their naturally occurring counterparts, DNA and RNA, according to a new study published today (April 19) in Science. The results of the research have implications not only for the fields of biotechnology and drug design, but also for research into the origins of life—on this planet and beyond.

“It’s a breakthrough,” said Gerald Joyce of The Scripps Research Institute in La Jolla, California, who was not involved in the study—“a beautiful paper in the realm of synthetic biology.”

“It shows that you don’t have to stick with the ribose and deoxyribose backbones of RNA and DNA in order to have transmittable, heritable, and evolvable information,” added Eric Kool of Stanford University, California, who also did not participate in the research.

Over the years, scientists have created a range of XNAs, in which the ribose or deoxyribose portions of RNA and DNA are replaced with alternative molecules. For example, threose is used to make TNA, and anhydrohexitol is used to make HNA. These polymers, which do not exist naturally, are generally studied with various biotechnological and therapeutic aims in mind. But some researchers, like Philipp Holliger of the MRC Laboratory of Molecular Biology in Cambridge, UK, think XNAs might also provide insights into the origins of life. They might help to answer questions such as, “why is life based on DNA and RNA, and, if we ever find life beyond earth, is it likely to be based on the same molecule or could there be other possibilities?” Holliger said.

To get at some of these questions, Holliger and his colleagues had to first create enzymes that could replicate XNAs, a necessary first step to evolution. They did this both by randomly mutating and screening existing DNA polymerases for their ability to read XNA, and by an iterative process of selecting polymerase variants with capacities for XNA synthesis. In the end, they had several polymerases that could synthesize six different types of XNA.