Which one of the following mRNA sequences can be translated completely ?

Options

A. AUG UUC UCC UGG UAA UAU
B. AUG UUC UCC UGA UGG UAU
C. AUG ACG UAU UUC UGA CUC
D. AUG UAU UUC UGC CUC UAG

Answer

To determine which mRNA sequence can be translated completely, we need to analyze the provided sequences for the presence of stop codons. Stop codons are specific sequences in mRNA that signal the termination of translation. The three stop codons are UAA, UAG, and UGA.

### Step-by-Step Solution:

1. **Identify the Stop Codons**:
- The three stop codons are UAA, UAG, and UGA. Any mRNA sequence containing these codons will terminate translation at that point.

2. **Examine Each mRNA Sequence**:
- We need to look at each mRNA sequence provided in the options and check for the presence of any stop codons.

3. **Analyze the First Sequence**:
- If the first sequence is AUG (Methionine), UUC (Phenylalanine), UUC (Phenylalanine), UGG (Tryptophan), UAA (Stop codon).
- Since UAA is present, this sequence cannot be translated completely.

4. **Analyze the Second Sequence**:
- If the second sequence contains UGA (Stop codon), then translation will stop here as well.
- Therefore, this sequence cannot be translated completely.

5. **Analyze the Third Sequence**:
- If the third sequence also contains UGA, it will similarly stop translation.
- Thus, this sequence cannot be translated completely.

6. **Analyze the Fourth Sequence**:
- If the fourth sequence does not contain any of the stop codons (UAA, UAG, UGA), it can be translated completely.
- Since there are no stop codons in between, this sequence is the only one that can be translated fully.

7. **Conclusion**:
- The fourth option is the correct answer as it does not contain any stop codons that would interrupt translation.

### Final Answer:
The mRNA sequence that can be translated completely is the fourth option.