Adding to the Genetic Alphabet

The genes carried on the DNA of every living thing are all made up of four molecules, known as bases: adenine (A), cytosine (C), guanine (G) and thymine (T). In groups of three, these bases form codons, which, in turn, make up the building blocks for all of the amino acids (and subsequently all of the proteins) found in nature. A total of 64 codons can be formed from these four bases. But scientists recently announced that they have added two more “letters” to the genetic alphabet, bringing the total number of potential codons to 216.

Some thirteen years ago, two synthetically engineered bases called “X” and “Y” were developed in the lab. In 2014, they were moved from the test tube into an E. coli cell, where the bacterium successfully copied the six-base DNA and passed it on to its offspring cells. Recently, the team was able to use the altered DNA to generate new proteins with chemical bonds unlike those previously seen in DNA.

This revolutionary development illustrates that the genetic code is expandable, adaptable and could have evolved in any number of ways. With new building blocks, it may be possible to create proteins that can do new things – such as developing improved therapies for cancer and autoimmune disorders or microorganisms that can break down pollutants into safer chemicals. Work is already underway by another team of researchers to recode E. coli with up to four artificial bases.