An Analysis of Single Nucleotide Substitution in Genetic Codons - Probabilities and Outcomes

Background: Single nucleotide substitutions (SNS) in genetic codon are of prime importance due to their ability to alter an amino acid sequence as a result. Given the nature of genetic code, any SNS is expected to change the protein sequence randomly into any of the 64 possible codons. In this paper, we present a theoretical analysis of how single nucleotide substitutions in genetic codon may affect resulting amino acid residue and what is the most likely amino acid that will get selected as a result. Methods: A probability matrix was developed showing possible changes and routes likely being followed as a result of base substitution mutation causing changes at the translational level for the amino acid being encoded. Results: We observe that in event of single base pair substitution in a given amino acid; a chosen set of amino acids is theoretically more probable to be resulted suggesting a directional rather than a random change. This study also indicates that for a given amino acid coded by a number of synonymous codons, all synonymous codons will result into same list of amino acids in case of all possible SNS at three positions. Conclusion: The present work has resulted into development of a theoretical probability matrix which can be used to predict changes in amino acid residues in a protein sequence caused by single base substitutions.