Protein Coding

Abstract

Abstract A protein‐coding gene is composed of a series of nucleotide triplets – the codons – that encrypt not only the protein content but also the start and stop signals. There are 64 (4 3 ) codons in the canonical genetic code, which encode 20 amino acids with redundancy. Hence, there are synonymous codons that encode the same amino acids, and they are used at different frequencies among different species. The resultant codon‐usage biases reveal complex interplays of mutation and selection. Protein‐coding genes can be organised into families of similar function, structure and sequence, according to their shared evolutionary histories. Individual proteins are modularly constructed of domains, which are often rearranged on evolutionary timescales to create functionally novel proteins. Key Concepts: A protein‐coding gene consists of a series of nucleotide triplets. The genetic code defines the relationship between codons and amino acids. The genetic code can be organised into two halves and four quarters, which manifest distinct physiochemical features. Codon usage bias, a phenomenon in which synonymous codons (encoding the same amino acid) are used at different frequencies in different species, is a result of complex interplays between mutation and selection. Protein‐coding genes are organised into families of similar function, structure and sequence, according to their shared evolutionary histories. Individual proteins are modularly constructed from domains, which are often rearranged on evolutionary timescales to create functionally novel proteins.