Which of the following serves as an stop codon ?

Options

A. UAG
B. AGA
C. AUG
D. GCG

Answer

To determine which of the following serves as a stop codon, we will analyze the given options: UAG, AGA, AUG, and GCG.

### Step-by-Step Solution:

1. **Understanding Stop Codons**:
- Stop codons are specific sequences of nucleotides in mRNA that signal the termination of protein synthesis during translation. They do not code for any amino acids and are also referred to as non-sense codons or termination codons.

2. **Identifying the Stop Codons**:
- There are three known stop codons in the genetic code:
- UAG (amber)
- UGA (opal)
- UAA (ochre)

3. **Analyzing the Options**:
- Now, let's look at the provided options:
- **UAG**: This is one of the recognized stop codons.
- **AGA**: This codon codes for the amino acid arginine and is not a stop codon.
- **AUG**: This codon is the start codon and codes for methionine, not a stop codon.
- **GCG**: This codon codes for the amino acid alanine and is not a stop codon.

4. **Conclusion**:
- Among the given options, the only codon that serves as a stop codon is **UAG**.

### Final Answer:
The correct answer is **UAG**.

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