Methionine is coded by:

Options

A. AUG
B. GUA
C. AGU
D. TUG

Explanation

To determine which codon codes for the amino acid methionine, we can follow these steps:

### Step 1: Understand the question
We need to identify the codon that corresponds to the amino acid methionine.

### Step 2: Know the options
The options provided are:
1. AUG
2. GUA
3. AGU
4. TUG

### Step 3: Recall the genetic code
The genetic code consists of codons, which are sequences of three nucleotides that correspond to specific amino acids. Methionine is one of the amino acids coded by a specific codon.

### Step 4: Identify the correct codon for methionine
From the genetic code, we know that:
- Methionine is coded by the codon **AUG**.

### Step 5: Confirm the role of AUG
AUG not only codes for methionine but also serves as the start codon in the process of translation, indicating where protein synthesis begins.

### Conclusion
The correct answer is **AUG**, which codes for methionine.

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