Final answer:
Codon bias is the preference for certain codons over others when encoding the same amino acid, often reflecting an organism's genomic nucleotide composition.
Step-by-step explanation:
Codon bias refers to the phenomenon where certain codons are used more frequently than others to encode the same amino acid. This bias is linked to an organism's genome nucleotide composition, such as preference for A-T or G-C-rich codons. It goes beyond the universal genetic code, indicating a non-random selection of codons across species, orders, and even within individual species. While the standard genetic code is degenerate, meaning an amino acid can be encoded by more than one codon, some organisms show preferences that mirror their genomic nucleotide content. This can have implications for mRNA stability, translation efficiency, and protein expression.
For example, organisms with AT-rich genomes tend to favor AT-rich codons, and those with GC-rich genomes prefer GC-rich codons. Given that synonymous codons can code for the same amino acid, this bias can affect translation and even the evolutionary process of organisms.