Life on Earth uses DNA and RNA to store and utilize genetic information, but what if there’s another way? A new analysis from researchers at Emory University and the Tokyo Institute of Technology suggests a plethora of molecules could serve the same basic task of organizing and storing genetic information. They estimate more than a million possible stand-ins for DNA, some of which could help us fight disease or help us know what to expect as we search for alien life.
DNA (and RNA) consist of several components that make up the familiar double helix. There are the base pairs like adenine and guanine, a sugar (deoxyribose for DNA and ribose for RNA), and a phosphate group. The sugar and phosphate give nucleic acid an alternating sugar-phosphate backbone. We already know there are many alternatives to the five bases at work in DNA and RNA on Earth, but the new study looks at how the scaffolding of nucleic acid could vary.
The team used a computer simulation to explore a so-called “chemical space” within certain constraints. To choose the constraints, the team had to distill what makes nucleic acid molecules distinct. They settled on organic molecules that can assemble into a linear polymer with at least two attachment points, plus a place for nitrogen bases to connect. The substructure of the molecule also needs to be stable in a polymer configuration. Since these molecules don’t contain the traditional sugars and phosphorus, you can’t call them DNA — they’re some other kind of nucleic acid with potentially similar properties.
A few alternate nucleic acids.
The analysis points to more than 1,160,000 potential nucleic acid molecules. That number exceeded even the most extreme estimates beforehand, but researchers can now start looking at these molecules in a laboratory setting to see if they can work as a DNA alternative. The team says this shows evolution on Earth may have experimented with several different molecular designs for storing genetic information before DNA ultimately won out.
Researchers around the world are working on therapeutic drugs that resemble nucleic acid, some of which could help combat viruses and cancer. A better understanding of these DNA alternatives could make those treatments more effective. And then there’s the importance to exobiology research. If we’re looking for evidence of extraterrestrial life, it might help to remember they could have genetic material using one of the other million possible molecules.
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