Question

According to Wobble hypothesis GCI present in anticodon arm of tRNA can bind to triplet codons present in mRNA are
(A). 5' CGA 3'
(B). 3' CGA 5'
(C). 5' CGU 3'
(D). 3' CGU 5'
Choose the correct answer from the options given below:

• A. (A) and (D) only.
• B. (A) and (C) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

According to Wobble Rules, the modified base Inosine (I) at the 5'-anticodon position is highly versatile and can pair with three different bases: U, C, or A in the mRNA codon.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Francis Crick's Wobble Hypothesis states that base pairing between the 3' codon base of mRNA and the 5' anticodon base of tRNA does not follow strict Watson-Crick rules, allowing a single tRNA to recognize multiple codons.

Step 2: Detailed Explanation:
1. The tRNA anticodon sequence is given as 5'-GCI-3'.
2. The first two positions (5'-GC... of the anticodon) form standard Watson-Crick base pairs with the last two positions of the mRNA codon: - G (at 1st position of anticodon) pairs with C (at 2nd position of codon).
- C (at 2nd position of anticodon) pairs with G (at 1st position of codon).
3. This means the corresponding mRNA codons must begin with 5'-CG...-3'.
4. The third position of the anticodon is Inosine (I). According to wobble rules, Inosine at the 5' position of the anticodon can pair with U, C, or A at the 3' position of the codon.
5. Therefore, the allowed codons are: - 5'-CGU-3' (Statement C)
- 5'-CGC-3'
- 5'-CGA-3' (Statement A)
6. Statements B and D write the sequences in the incorrect 3'-to-5' direction, which does not match these codons.

Step 3: Final Answer:
The complementary codons are (A) and (C) only.