Andrew Brookes/Plainpicture
THE genetic alphabet just got 50 per cent bigger. A bacterium has been engineered not only to have two more “letters” in its DNA, but to use them to make new proteins that have never existed in nature.
The genes carried on DNA are instruction manuals for making proteins, which do essential jobs like digesting food and fighting infection. The letters that make up the genetic code are molecules called bases. All known living things use the same four letters: A, C, G and T.
The new bacterium has two more synthetically engineered bases, called “X” and “Y”.
Floyd Romesberg at the Scripps Research Institute in La Jolla, California, and his team have been working on X and Y for 13 years. In 2014, they moved them from a test tube into an E. coli bacterium. The cell was able to copy the DNA