As you know, in order to encodea huge amount of information in the genetic code, only 4 nucleic acids are used: adenine, guanine, thymine and cytosine. In the genetic code, they are denoted by the corresponding letters - A, G, T, and C. Thus, we can say that the “genetic alphabet” consists of 4 letters, and until recently it was believed that it could not be changed, however, a group of scientists from the Scripps Institute for the first time managed to supplement it with two new letters and at the same time leave it fully functioning.
In all living organisms, the nucleic acids described aboveacids are connected to each other not anyhow, but according to the principle of complementarity. That is, they “look” at each other, as it were, and opposite to A there should always be T, and opposite to G - Ts, and nothing else. But this is still half the battle. These letters should "form words", which are called triplets - special combinations, due to which all the main points occur, such as reading information, encoding proteins and so on. A few years ago, Science magazine published an article describing an experiment in which transport RNAs brought a new amino acid to DNA that was recognized and embedded in code. Moreover, this acid was only one, did not have a pair and did not perform a new function.
In the new survey, researchers from the companySynthorx used two new nitrogenous bases (designated X and Y). They are located opposite each other in the double-stranded DNA molecule, like the standard 4 bases, but, unlike them, the “new letters” are connected not by hydrogen bonds, but by hydrophobic ones. Moreover, by incorporating two new bases into the DNA of bacteria, the latter were able to reproduce them, but such bacteria initially shared more slowly than usual and sometimes replaced the new DNA with “traditional” one. Bacteria that reproduce new DNA without problems have already been bred. It remains only to come up with new letters for these triplets.
“If you count how many triple combinationscan be obtained by holding four letters, we get 64 combinations, and by adding only two letters, we expand the number of possible genetic words to 216, and as a result it will be possible to code another 172 amino acids, which opens up simply endless scope for bioengineering ” .