Which of the following base sequences is used during translation?

Question

BlackTom AI · Accepted Answer

Start and stop codons in mRNA specify the exact points where ribosomes begin and end polypeptide synthesis, so they are the sequences used during translation.

1. Relevant knowledge points and concepts
- Translation is the process by which ribosomes read messenger RNA (mRNA) codons to synthesize a polypeptide. 
- A start codon (typically AUG in mRNA) signals the ribosome to initiate translation and also codes for methionine. 
- Stop codons (UAA, UAG, UGA) do not code for amino acids; they signal termination and release of the completed polypeptide. 
- Promoters and terminators are DNA sequence elements involved in transcription initiation and termination, not directly read by ribosomes. 
- The polyadenylation signal (AAUAAA in eukaryotic pre-mRNA) directs mRNA processing (cleavage and poly-A tail addition), not the ribosome’s reading frame.

2. Step-by-step reasoning
- Identify which molecular machine is active during translation: the ribosome reading mRNA codons.
- Determine which sequences are read by ribosomes: codons within the mRNA.
- Match each answer option to its role: promoters/terminators control transcription, start/stop codons control translation, polyadenylation signals control mRNA processing.

3. Calculations/intermediate steps
- No numerical calculations are required. Logical mapping: (ribosome reads codons on mRNA) → (start and stop codons are codons on mRNA) → therefore they are used in translation.

4. Why the correct answer is correct
- Start and stop codons are actual codons on the mRNA that direct ribosomes where to begin and end polypeptide synthesis, so they are the sequences used during translation.

5. Why other options are incorrect
- a. Promoter and terminator: function in transcription (DNA → RNA), not in translation. 
- c. Polyadenylation signal: functions in mRNA processing (cleavage and poly-A addition), not as ribosome signals. 
- d. Both a and b: incorrect because promoters/terminators are not used during translation, so “both” cannot be correct.

6. Conclusion
Therefore, the correct answer is b. Start and stop codons, which matches the provided answer.

Which of the following base sequences is used during translation?单项选择题

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