Mysteriously, Our Genetic Code Stopped Evolving 3 Billion Years Ago


According to researchers, our genetic code stopped evolving 3 billion years ago, but why? When Francis Crick described the Genetic code back in the 1960s, the mysterious halt in the evolution of the Genetic Code was referred to him as a frozen accident.

Scientists might have solved the question of the century. According to experts, the genetic code’s limit was reached 3 billion years ago when evolution came to a sudden halt.

Even though life on our planet continues to evolve, the genetic code, that mystery machine which drives life has remained static using the same ‘commands’ and components in the same way it did in the distant past, billions of years ago.

It is known that at a certain point in our planet’s long history, our genetic code’s evolution came to a halt when it reached its plateau, thus preventing further development of the code. For decades, Scientists had no clue why, but now, thanks to a new study, researchers believe that the evolution of our genetic code came to a halt because of limitations in the way our DNA is translated to make proteins.

In order to understand it, researchers from Spain focuses on a molecule called transfer RNA (tRNA).

Basically, tRNA has the job to move the building blocks of proteins to the assembly line in order for them to be linked together in an appropriate way.

Interestingly when Francis Crick described the Genetic code back in the 1960s, the mysterious halt in the evolution of the Genetic Code was referred to him as a frozen accident.

Scientists believe this is because the genetic code evolved only enough to account for 20 amino acids, which are the building blocks of proteins. The Genetic Code eventually reached a point where it was unable to alter, or expand so it could account for more than 20 amino acids, which caused it to remain static or frozen in time for billions of years.

The human body can link available amino acids together in order to make proteins, but it uses additional amino acids which are not included in the genetic code, relying on complicated chemical channels.

Interestingly, researchers say that our Genetic Code could have developed to use up to 63 Amino Acids, but for some reason, it stopped at 20. Experts believed that if the ‘machinery’ that reads the DNA and translates it to proteins were to include more than 20 amino acids, it is very likely that numerous mistakes would have been present, leading to an eventual meltdown of the biological system.

Professor Lluís Ribas de Pouplana, a geneticist from the Institute for Research in Biomedicine (IRB Barcelona) and senior author of the study, said: „Protein synthesis based on the genetic code is the crucial feature of biological systems, and it is critical to ensure faithful translation of information.“

Every single transfer RNA has two central regions which link it to a specific amino acid at one end. The other recognises a three-letter stamp of the genetic code. Scientists say that multiple genetic stamps can code for the same amino acids, and the combination of these areas are what gives each tRNA an identity.


Speaking to MailOnline, Professor Ribas said: „Our work shows that the central pieces of the genetic code, the transfer RNAs, can not house enough specific identity elements for the system to be able to distinguish 63 of them. Since you need a new tRNA for each new amino acid, once the limit of tRNAs is reached that determines how many amino acids you can use. This limit happened to be at 20, and it hasn’t changed for 3 billion years.“

Scientists are now looking for ways to overcome the limitations set in place billions of years ago with the help of synthetic biology.

„It is thus unlikely that the limit will change naturally, and you could certainly call it a bottleneck for molecular diversity. Artificially, however, we are able to increase the number of amino acids used by cells under controlled laboratory conditions. I think that our work adds to the notion that adding new amino acids in a natural context would require very dramatic engineering of the system. Something that nature can’t do. How to go about this engineering is the main question that opens after our study.“ Said Professor Ribas in the interview.


Saturation of recognition elements blocks evolution of new tRNA identities | Science Advances