Question

CCA 3' end of tRNA is called as

• A. Anticodon loop
• B. DHU loop
• C. T $\psi$ C
• D. Amino acid binding site

Answer 1

The correct option is D Amino acid binding site

All tRNAs have about 73 to 93 nucleotides that fold into four base-paired stems and three loops, a structure which looks like a clover leaf in secondary structure. The anticodon loop has triplet at the tip which base pairs with the corresponding codon in mRNA; option A is incorrect. Transfer-RNA has 7-15% post-transcriptionally modified bases. Dihydrouridine (D) is nearly always found in the D loop and ribothymidine (T) and pseudouridine in the T psi C loop. The D loop serves as Aminoacyl synthetase recognition and binding loop while the T psi C loop binds the charged tRNA-amino acid to ribosome. This makes options B and C incorrect. The 3' end has CCA sequence. Attachment of an amino acid to the 3’ adenosine yields an aminoacyl-tRNA and therefore the CCA site is called amino acid binding site; option D is correct.