Correct option is B
Explanation-
Aminoacyl-tRNA synthetases are enzymes that match each tRNA with its correct amino acid. This process is highly specific and essential for the accuracy of protein synthesis. While anticodon recognition is important, not all aminoacyl-tRNA synthetases rely exclusively on the anticodon. In many tRNAs, other structural elements such as the acceptor stem, D-loop (DHU loop), and TψC loop are also crucial for recognition.
So, the correct answer is option b - Aminoacyl-tRNA synthetases recognize their cognate tRNAs by recognition of their anticodons in some tRNAs only.
Incorrect options-
Option a - Aminoacyl-tRNA synthetases recognize their cognate tRNAs by the exclusive recognition of their anticodons.
Recognition is not exclusively based on anticodons. Other features like the acceptor stem, TψC loop, and D-loop are often more critical.
Option c - Aminoacyl-tRNA synthetases cannot aminoacylate a tRNA that lacks the conserved modifications in the TψC loop.
While the TψC loop is important for tRNA stability and structure, modifications there are not always essential for aminoacylation. Some synthetases can still recognize and aminoacylate a tRNA even if certain modifications are missing.
Option d - Aminoacyl-tRNA synthetases cannot aminoacylate a tRNA that lacks the conserved modifications in the DHU loop.
Similar to Option c, the DHU loop contributes to folding and identity, but not all modifications are essential. Some synthetases rely on other structural signals beyond DHU loop modifications.
