A point mutation changes the codon GAA (glutamic acid) to GAG (glutamic acid) in the mRNA of a gene coding for an enzyme. Explain why this mutation is silent and discuss its possible impact if it occurs in a highly conserved region of the protein.
Answer
Silent because both codons code for glutamic acid; however, if in a conserved region it could still affect protein folding or stability, possibly reducing enzyme activity.
Step-by-step solution
- Identify the original codon GAA and the mutant codon GAG.
- Consult the genetic code: both GAA and GAG translate to glutamic acid.
- Conclude that the mutation is silent at the amino‑acid level.
- Recognize that highly conserved regions are functionally critical.
- Explain that a silent mutation can alter mRNA secondary structure or translation efficiency.
- Note that changes in folding or stability may reduce enzyme activity even though the amino acid is unchanged.
Common mistake: Assuming silent mutations always have no effect
Concept tested: Silent mutation consequences
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