Describe the structure of tRNA with a diagram.

Explanation

(i) The transfer RNA, (tRNA) molecule of a cell acts as a vehicle that picks up the amino acids scattered through the cytoplasm and also reads specific codes of mRNA molecules. Hence it is called an adapter molecule. This term was postulated by Francis Crick.
(ii) The two dimensional clover leaf model of tRNA was proposed by Robert Holley. The secondary structure of tRNA depicted in the following picture looks like a clover leaf.
(iii) In actual structure, the tRNA is a compact molecule which looks like an inverted L.
(iv) The clover leaf model of tRNA shows the presence of three arms namely DHU arm, middle arm and T`Psi`C arm.
(v) These arms have loops such as amino acyl binding loop, anticodon loop and ribosomal binding loop at their ends. In addition it also shows a small lump called variable loop or extra arm.
(vi) The amino acid is attached to one end (amino acid acceptor end) and the other end consists of three anticodon nucleotides.
(vii) The anticodon pairs with a codon in mRNA ensuring that the correct amino acid is incorporated into the growing polypeptide chain.
(viii) Four different regions of double-stranded RNA are formed during the folding process. Modified bases are especially common in tRNA.
(ix) Wobbling between anticodon and codon allows some tRNA molecules to read more than one codon.