A Search for the Physical Basis of the Genetic Code.

A Search for the Physical Basis of the Genetic Code. Genetic code is one of the greatest mysteries of biology: it is shared by basically every living organism on this planet, with little to none differences between species that can be very far away from each other from an evolutionary point of view. Not only organisms share similar DNA structures and protein synthesis methods: the translation from a base triplet to the respective amino acid, i.e the genetic code, is found to be surprisingly consistent among all living creatures. The genetic code is not only stable between different species, but also through millions of years of evolution: it has been almost identical to itself for a very long time. Researchers strongly believe that there must be a reason behind this: “survival of the fittest” is a widely known expression that states that during evolution only the most suit survives and keeps on proliferating, which hints that there must have been some force pushing all organisms to adopt this code. This concept is also known as “evolutionary pressure”: it can be given by external factors like the environment, but also by some intrinsic quality of the genetic code itself. Unfortunately, despite all the resources spent on this topic and the researchers that were and are spending time to solve this mystery, genetic code does not seem to be willing to cooperate and no one has been able to really give an explanation to its almost omnipresence in our world. This work aims to analyse the genetic code from two different points of view: on the first hand, entropy is checked as a primary indicator of the genetic code characteristics, then its stability is evaluated and compared to other possible codes. 36 different genomes from GenBank have been studied using Matlab to understand whether its characteristics can be better understood. This study is hence approaching the problem from a mathematical and statistical point of view, partially ignoring the biochemical pathways that take place inside living organisms. In the first part, entropy of mutated genetic sequences is studied to determine whether genetic code is also a way living organisms use to decrease this quantity. Then, a fitness function will be used to investigate robustness of the code to mutations and mistranslations