Question

Which codon has a dual function?

• A. \( \text{AUG} \)
• B. \( \text{UAG} \)
• C. \( \text{UAA} \)
• D. \( \text{UGA} \)

Hint:

Remember, \( \text{AUG} \) initiates protein synthesis and codes for methionine. This dual role is a cornerstone of translation in all organisms.

Answer 1

The Correct Option is A

The codon \( \text{AUG} \) has a dual function in translation:
It serves as the start codon, signaling the initiation of protein synthesis. This is the site where ribosomes begin translation by recruiting the tRNA carrying methionine.
It codes for the amino acid methionine (in eukaryotes) and \( \text{N-formylmethionine (fMet)} \) in prokaryotes.
Other codons such as \( \text{UAG}, \text{UAA}, \text{UGA} \) are stop codons and do not perform any dual role. They terminate translation by signaling the ribosome to release the polypeptide chain. --- Why \( \text{AUG} \) is unique? \begin{itemize}
\( \text{AUG} \) is recognized universally across prokaryotic and eukaryotic organisms as the start codon.
Its dual role is a result of its unique ability to recruit both initiation factors for translation and tRNAs carrying methionine. \end{itemize} ---
Final Answer: \[ \boxed{\text{AUG}} \]