What is codon bias? If synonymous substitutions give the same amino acid, why should there be a bias in which codons encode that amino acid?
What will be an ideal response?
Codon bias is the disproportionate use of certain synonymous codons over others. Some synonymous codons pair with different tRNAs that carry the same amino acid. One explanation for this concerns efficiency in translation: While a mutation to a synonymous codon does not change the amino acid, it may change the tRNA used by a ribosome during translation. Over evolutionary time, natural selection may favor use of codons corresponding with the most readily available tRNA.
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