Initiator codon in eukaryotes

Options

A. GUG
B. AUG
C. UAG
D. UGA

Answer

**Step-by-Step Solution:**

1. **Understanding Initiator Codons**: In eukaryotic cells, the initiator codon is the specific codon that signals the start of translation, which is the process of synthesizing proteins from mRNA.

2. **Identifying the Initiator Codon**: The primary initiator codon in eukaryotes is AUG. This codon is crucial because it not only marks the beginning of the translation process but also codes for the amino acid methionine.

3. **Dual Function of AUG**: The AUG codon serves two important roles:
- It acts as the start signal for translation.
- It codes for the first amino acid (methionine) in the newly synthesized polypeptide chain.

4. **Exclusion of Other Codons**: Other codons such as GUG, UAG, and UGA do not serve as initiator codons in eukaryotes.
- GUG can sometimes act as a start codon in certain contexts but is not the primary initiator codon.
- UAG and UGA are stop codons, which signal the termination of protein synthesis.

5. **Conclusion**: Therefore, the correct answer to the question regarding the initiator codon in eukaryotes is AUG.

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