SUMMARY
Mutations underpin the process of life1, be it beneficial or detrimental. While mutations are assumed to be random in the lack of selection pressures2, the genetic code underlies computable probabilities in amino acid phenotypic changes. Certain codons were found to require less mutational events to lead to specific amino acids than others. With applications in drug resistance3,4, studying the probability of amino acid changes are important. In this study, we calculated the probabilities of substitutions mutations in the genetic code leading to the 20 amino acids and stop codons. Our calculations allow us to uncover an in-built self-preservation organization of the genetic code that steers away from disruptive changes at the amino acid level, away from start, aromatic, negative charged amino acids and stop codons. Our findings here provide the baseline mutational probability to study the genetic code mutations.