Four dating bases
The study implies that there is nothing particularly “magic” or special about those four chemicals that evolved on Earth, says Romesberg. Normally, as a pair of DNA strands twist around each other in a double helix, the chemicals on each strand pair up: A bonds to T, and C bonds with G.
For a long time, scientists have tried to add more pairs of these chemicals, also known as bases, to this genetic code.
The DNA of life on Earth naturally stores its information in just four key chemicals — guanine, cytosine, adenine and thymine, commonly referred to as G, C, A and T, respectively.
Now scientists have doubled this number of life’s building blocks, creating for the first time a synthetic, eight-letter genetic language that seems to store and transcribe information just like natural DNA.
This is a substantial advance, says Philipp Holliger, a synthetic biologist at the MRC Laboratory of Molecular Biology in Cambridge, UK, because other methods of expanding the genetic alphabet are not as structurally sound.
Other groups have followed, with Romesberg’s lab making headlines in 2014 after inserting a pair of unnatural bases into a living cell.
The researchers call the resulting eight-letter language ‘hachimoji’ after the Japanese words for ‘eight’ and ‘letter’.
The additional bases are each similar in shape to one of the natural four, but have variations in their bonding patterns.
By adjusting these holes and prongs, the team has come up with several new pairs of bases, including a pair named S and B, and another called P and Z.
In the latest paper, they describe how they combine these four synthetic bases with the natural ones.