Question

Identify the labels $A,B,C$ and $D$ in the given structure of $tRNA$ and select the correct option.

	A	B	C	D
(a)	Anticodon loop	$T\Psi C$ loop	AA binding site	DHU loop
(b)	AA binding site	$T\Psi C$ loop	Anticodon loop	DHU loop
(c)	AA binding site	DHU loop	Anticodon loop	$T\Psi C$ loop
(d)	AA binding site	DHU loop	$T\Psi C$ loop	Anticodon loop

• A. a
• B. b
• C. c
• D. d

Answer 1

Answer: (B)

In $tRNA$, there is a $T\Psi C$ loop which contains pseudouridine and ribothymidine. The loop is the site for attaching to ribosomes. Another loop, $DHU$ loop contains dihydrouridine. It is binding site for aminoacyl synthetase enzyme. $tRNA$ molecules have unpaired (single stranded) $CCA-OH$ sequence at the $3^{\prime }$ end. This is called amino acid binding site, because the amino acid becomes covalently attached to adenylic acid or $A$ of $CCA$ sequence during polypeptide synthesis. Anticodon loop is made up of three nitrogen bases for recognising and attaching to the codon of $mRNA$.