USA Biology Olympiad (USABO) Practice Exam

What does the poor representation of the arginine codon AGG in E.coli genes suggest?

1. It may have a regulatory function in the cell

2. It is preferentially avoided during protein synthesis

3. It is involved in codon bias selection

4. It is less efficient than other codons

The correct answer is: It may have a regulatory function in the cell

The poor representation of the arginine codon AGG in E. coli genes suggests that it may have a regulatory function in the cell. In bacteria, the usage frequency of certain codons can be influenced by the availability of specific tRNA molecules that correspond to those codons. If AGG is underrepresented, it likely indicates that it is not favored in translation due to potential regulatory mechanisms. This could mean that the cell has evolved to optimize protein synthesis using more abundant codons that correspond to more available tRNAs, thus enhancing overall translational efficiency and control over gene expression. The usage patterns of codons can also indicate evolutionary pressures and may signal the codon's role in metabolic or regulatory pathways, leading to the conclusion that AGG might have a specific function beyond just coding for arginine.