If the base sequence of a codon in mRNA is `5'-AUG-3'`, the sequence of tRNA pairing with it must be

Options

A. 5' - UAC - 3'
B. 5' - CAU - 3'
C. 5' - AUG - 3'
D. 5' - GUA - 3'

Answer

To solve the question, we need to determine the sequence of tRNA that pairs with the mRNA codon `5'-AUG-3'`. Here’s a step-by-step breakdown of how to arrive at the correct answer:

### Step-by-Step Solution:

1. **Identify the mRNA Codon**: The given mRNA codon is `5'-AUG-3'`.

2. **Understand Codon-Anticodon Pairing**: In the process of translation, the anticodon on the tRNA pairs with the codon on the mRNA. The pairing is based on complementary base pairing rules:
- Adenine (A) pairs with Uracil (U) in RNA.
- Uracil (U) pairs with Adenine (A).
- Cytosine (C) pairs with Guanine (G).
- Guanine (G) pairs with Cytosine (C).

3. **Determine the Anticodon Sequence**: The anticodon must be complementary to the mRNA codon. Since the mRNA codon is `5'-AUG-3'`, we need to find the complementary bases:
- The first base of the codon (A) pairs with U.
- The second base (U) pairs with A.
- The third base (G) pairs with C.

4. **Write the Anticodon**: The complementary bases give us the sequence `3'-UAC-5'`. However, since we need to express the tRNA sequence in the 5' to 3' direction, we reverse this sequence to get `5'-CAU-3'`.

5. **Final Answer**: Therefore, the sequence of tRNA pairing with the mRNA codon `5'-AUG-3'` must be `5'-CAU-3'`.