Q24 — Codon Usage Bias

Theoretical A Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license

While central dogma claims that synonymous substitutions (which do not change the primary sequence of the polypeptide) do not have any effect on protein sequence and its cellular function, codons are not used to the same extent in the vast majority of sequenced genomes. This is known as the codon usage bias. For example, among four codons that encode glycine in Escherichia coli, GGU and GGC have higher abundance than GGA and GGG codons. The primary driver for such unequal codon usage is to match the available pool of tRNA molecules.

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. Protein coding genes that are involved in ribosomal assembly have very high codon usage bias.

B. Transgenic material that was not corrected for codon usage bias of the recipient's genome will have lower translational efficiency relative to the corrected one.

C. Codon usage bias is not found in viruses.

D. Methionine will have one of the strongest codon usage biases because it is always the first amino acid in the protein.

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Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)