More than four possible bases, more coverage

Scientists Have Created Synthetic DNA with 4 Extra Letters

A couple billion years ago, four molecules danced into the elegant double-helix structure of DNA, which provides the codes for life on our planet. But were these four players really fundamental to the appearance of life — or could others have also given rise to our genetic code?

A new study, published today (Feb. 20) in the journal Science, supports the latter proposition: Scientists have recently molded a new kind of DNA into its elegant double-helix structure and found it had properties that could support life.

But if natural DNA is a short story, this synthetic DNA is a Tolstoy novel.

The researchers crafted the synthetic DNA using four additional molecules, so that the resulting product had a code made up from eight letters rather than four. 

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Extended genetic alphabet covered in New York Times

DNA Gets a New — and Bigger — Genetic Alphabet

DNA is spelled out with four letters, or bases. Researchers have now built a system with eight. It may hold clues to the potential for life elsewhere in the universe and could also expand our capacity to store digital data on Earth.

In 1985, the chemist Steven A. Benner sat down with some colleagues and a notebook and sketched out a way to expand the alphabet of DNA. He has been trying to make those sketches real ever since.

On Thursday, Dr. Benner and a team of scientists reported success: in a paper, published in Science, they said they have in effect doubled the genetic alphabet.

Natural DNA is spelled out with four different letters known as bases — A, C, G and T. Dr. Benner and his colleagues have built DNA with eight bases — four natural, and four unnatural. They named their new system Hachimoji DNA (hachi is Japanese for eight, moji for letter).

Crafting the four new bases that don't exist in nature was a chemical tour-de-force. They fit neatly into DNA’s double helix, and enzymes can read them as easily as natural bases, in order to make molecules.

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Synthetic DNA is a new technology and probably needs some new rules

Opinion: Ethical Boundaries Needed on the Uses of Synthetic DNA

A newly expanded genetic alphabet that includes four synthetic nucleotides highlights the need for strict boundaries on their use.

A study published last week expands the redesign of the 4-billion-year-old genetic code from a four-nucleotide base-pair alphabet to an eight-base-pair alphabet by incorporating artificial nucleotides. The scientists, led by Steven Benner of the Foundation for Applied Molecular Evolution and Firebird Biomolecular Sciences in Florida, have also identified a bacteriophage RNA polymerase variant that transcribes the synthetic DNA into synthetic RNA.  

Previously, a scientific team led by Floyd Romesberg at The Scripps Research Institute used its own synthetic base pairs to create bacteria that replicate the artificial DNA, translate the DNA into mRNA, and create new types of amino acids. 

These are technologically impressive accomplishments and the translational applications of these discoveries could be revolutionary.

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Four new bases available for synthetic biology (original article)

Hachimoji DNA and RNA: A genetic system with eight building blocks

Expanding the genetic code

DNA and RNA are naturally composed of four nucleotide bases that form hydrogen bonds in order to pair. Hoshika et al. added an additional four synthetic nucleotides to produce an eight-letter genetic code and generate so-called hachimoji DNA. Coupled with an engineered T7 RNA polymerase, this expanded DNA alphabet could be transcribed into RNA. Thus, new forms of DNA that add information density to genetic biopolymers can be generated that may be useful for future synthetic biological applications.

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