CodonNutzung

CodonNutzung (German for "codon usage") denotes the frequencies with which synonymous codons are used in the coding sequences of an organism. Because most amino acids are encoded by more than one codon, different species, genes and genomic regions exhibit characteristic preferences, commonly called codon bias. Patterns of codon usage arise from a combination of mutation biases, natural selection for translational efficiency and accuracy, genetic drift, and constraints related to GC content.

Empirical measures of CodonNutzung include the Codon Adaptation Index (CAI), relative synonymous codon usage (RSCU), and the effective number of codons (Nc). These indices are used to compare genes within and between genomes, to infer expression levels, and to detect horizontally transferred sequences or rapidly evolving regions. Codon preferences correlate with tRNA abundance in many organisms, so matching codon choice to the host tRNA pool can increase translation speed and protein yield; conversely, rare codons can induce translational pausing that affects folding.

Applications of CodonNutzung span molecular biology, biotechnology and evolutionary genomics. In heterologous gene expression and vaccine design, codon optimization adapts sequences to a chosen expression host to improve product levels. In comparative genomics, codon usage informs models of genome evolution and adaptation. Practical use requires caution: context effects such as mRNA secondary structure, regulatory motifs and translational kinetics mean that simple codon substitution can have unintended consequences.