Question

Which amino acid will be charged on the tRNA with anticodon 5Õ-GUU-3Õ?

• A. Asparagine (codon AAC)
• B. Valine (codon GUU)
• C. Leucine (codon UUG)
• D. Glutamine (codon CAA)

Hint:

Always write out the $5'$ and $3'$ ends explicitly when pairing codon and anticodon.
$5'\text{-GUU-}3'$ (anticodon) pairs with $3'\text{-CAA-}5'$ (codon), which is read as $5'\text{-AAC-}3'$ (Asparagine) from left to right.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
During translation, a tRNA molecule brings a specific amino acid to the ribosome. The identity of this amino acid is determined by the mRNA codon that pairs with the tRNA's anticodon through complementary, antiparallel base pairing.
Step 2: Detailed Explanation:
The question gives us the sequence of the tRNA anticodon written in the standard 5' to 3' direction:
\[ \text{Anticodon:} \quad 5'\text{-GUU-}3' \]
Because nucleic acid strands pair in an antiparallel orientation, we first rewrite this anticodon in the 3' to 5' direction:
\[ \text{Anticodon:} \quad 3'\text{-UUG-}5' \]
Next, we find the complementary mRNA codon by applying standard Watson-Crick base pairing rules (A pairs with U, and G pairs with C):
- The 3'-U pairs with 5'-A
- The middle U pairs with A
- The 5'-G pairs with 3'-C
Writing out the matching pairs in the correct antiparallel mRNA direction (5' to 3'):
\[ \text{Codon:} \quad 5'\text{-AAC-}3' \]
Now, let us examine the options provided. Option (A) links the codon 5'-AAC-3' to Asparagine.
Self-Correction / Re-verification: Let us check the codon options listed in the parentheses of the question text to see which one perfectly matches our derived 5'-AAC-3' codon:
- Option (A) explicitly states: Asparagine (codon AAC).
Therefore, the tRNA carries the amino acid Asparagine, which corresponds to the mRNA codon 5'-AAC-3'.
Step 3: Final Answer:
The amino acid charged on the tRNA is Asparagine (codon AAC).