AIIMS 2003 Botany tRNA structure MCQ Question

Explanation of tRNA and the Question:

Transfer RNA (tRNA) plays a crucial role in the process of translation during protein synthesis. Each tRNA molecule carries a specific amino acid and has an anticodon region that can base-pair with a corresponding codon on messenger RNA (mRNA). Let’s analyze the options provided in the question.

Correct Answer: A) (a) it binds with an amino acid at its 3' end

This statement is accurate. The structure of tRNA includes an acceptor stem at its 3' end, where an amino acid is covalently attached. The amino acid is linked to the tRNA at the 3' hydroxyl (-OH) group of the terminal adenosine nucleotide. This attachment is facilitated by specific enzymes called aminoacyl-tRNA synthetases, which ensure that the correct amino acid is attached to the corresponding tRNA. Thus, option A is true.

Clarification of Other Options:

B) (b) it has five double stranded regions

This statement is incorrect. While tRNA does have regions where base pairing occurs, leading to a stable three-dimensional structure, it does not have five distinct double-stranded regions. tRNA typically contains three double-stranded regions formed through intramolecular hydrogen bonding, which contribute to its cloverleaf structure. Therefore, this option is misleading regarding the number of double-stranded segments.

C) (c) it has a codon at one end which recognizes the anticodon on messenger RNA

This statement is also incorrect. In tRNA, the anticodon is the three-nucleotide sequence that pairs with the codon on mRNA during translation. The codon is a part of the mRNA, not the tRNA. Therefore, tRNA does not have a codon at one end; instead, it has an anticodon that is complementary to the mRNA codon. This option confuses the roles of mRNA and tRNA.

D) (d) it looks like clover leaf in the three-dimensional structure

While it is true that tRNA has a cloverleaf structure in its two-dimensional representation due to the folding and base pairing, the statement is somewhat misleading when referring to its three-dimensional structure. In three dimensions, tRNA does not retain a simple cloverleaf shape; it folds into a more complex L-shape. This three-dimensional conformation is crucial for its function in the ribosome during translation. Therefore, while partially true, this option does not accurately describe the tRNA's structure in three dimensions.

Conclusion:

In summary, the correct answer is A) (a) it binds with an amino acid at its 3' end. This is a fundamental aspect of tRNA's structure and function. Options B, C, and D contain inaccuracies or misleading statements regarding the structure and role of tRNA. Understanding the specific functions and characteristics of tRNA is vital for grasping the broader concepts of genetics and molecular biology.