Which triplet genetic codon on the mRNA molecule has dual functions?

Options

A. UUU
B. AUG
C. UGG
D. Both (1) and (3)

Answer

To solve the question "Which triplet genetic codon on the mRNA molecule has dual functions?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Codons**:
- Codons are sequences of three nucleotides on mRNA that correspond to specific amino acids or signal the termination of protein synthesis. There are a total of 64 possible codons.

2. **Identify the Types of Codons**:
- Out of the 64 codons, 61 codons code for amino acids, while 3 codons are stop codons (UAA, UAG, UGA) that signal the termination of protein synthesis.

3. **Look for Dual Functionality**:
- The question asks for a codon that has dual functions. This means it should serve two roles in the process of protein synthesis.

4. **Examine the Initiator Codon**:
- The codon AUG is known to have a dual function. It serves as the start codon (initiator) for protein synthesis and also codes for the amino acid methionine.

5. **Confirm Other Codons**:
- Other codons such as UUU (which codes for phenylalanine) and UGG (which codes for tryptophan) do not have dual functions; they only code for one specific amino acid.

6. **Conclude the Answer**:
- Since AUG is the only codon that acts both as an initiator and codes for methionine, it is the correct answer to the question.

### Final Answer:
The triplet genetic codon on the mRNA molecule that has dual functions is **AUG**.

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