The template strand of a gene reads 3′-TACGGA-5′. Given that the mRNA codons AUG and CCU code for methionine and proline respectively, what is the amino acid sequence of the polypeptide?
Answer and explanation
Correct answer: D. Methionine then proline
- Step 1: mRNA is complementary to the template: 3′-TAC GGA-5′ gives 5′-AUG CCU-3′.
- Step 2: AUG codes for methionine and CCU for proline, read in order from the 5′ end.
Answer
Methionine then proline.
Why not the others: Proline then methionine: the order of the codons was reversed. Methionine then glycine: only the first codon matches. No polypeptide: AUG is a start codon so translation proceeds.
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