Jordana Cepelewicz writes:

All life on Earth rests on the same foundation: a four-letter genetic alphabet spelling out a repertoire of three-letter words that specify 20 amino acids. These basic building blocks — the components of DNA and their molecular interpreters — lie at biology’s core. “It’s hard to imagine something more fundamental,” said Floyd Romesberg, a synthetic biologist at the pharmaceutical company Sanofi.

Yet life’s foundational biochemistry can be full of surprises. A few decades ago, researchers found viruses that had swapped one of the four bases in their DNA for a novel fifth one. Now, in a trio of papers published in Science in April, three teams have identified dozens of other viruses that make this substitution, as well as the mechanisms that make it possible. The discoveries raise the thought-provoking possibility that this kind of fundamental genomic change could be much more widespread and important in biology than anyone imagined.

“Here was this wonderful validation that right under our noses, nature has been expanding,” said Stephen Freeland, a biologist at the University of Maryland, Baltimore County.

“It really speaks to the adaptability of the genetic alphabet,” Romesberg said. [Continue reading…]