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 given sequences based on the rules of translation.

### Step-by-Step Solution:

1. **Understand the Translation Process**:
- Translation is the process of converting mRNA into a protein. It begins with a start codon (AUG) and ends with a stop codon (UAA, UAG, UGA).

2. **Identify the Start Codon**:
- The start codon is AUG, which codes for the amino acid methionine. This codon must be present at the beginning of the sequence for translation to initiate.

3. **Identify the Stop Codons**:
- The stop codons are UAA, UAG, and UGA. These codons signal the end of translation and do not code for any amino acids.

4. **Evaluate Each mRNA Sequence**:
- **Sequence 1**: AUG UUC UCC UGG UAA
- Starts with AUG (methionine) but ends with UAA (stop codon). Translation stops here, so it does not translate completely.
- **Sequence 2**: AUG UUC UCC UGA UGG UAU
- Starts with AUG (methionine) and continues translating until UAU, which is a stop codon. This sequence translates completely.
- **Sequence 3**: AUG ACG UAU UUC UGA CUC
- Starts with AUG but does not have a stop codon at the end. This sequence does not translate completely.
- **Sequence 4**: AUG UAU
- Starts with AUG but immediately encounters UAU, which is a stop codon. This sequence does not translate completely.

5. **Conclusion**:
- The only sequence that translates completely is **Sequence 2**: AUG UUC UCC UGA UGG UAU.

### Final Answer:
- The mRNA sequence that can be translated completely is **Sequence 2**.