Describe $tRNA$ as adapter molecule.
 

The presence of an adapter molecule which could read the code and would bind to specific amino acids during translation was proposed by Francis Crick in $1961 .$

tRNA was known before genetic code and was called $sRNA$ (soluble $RNA$) but later its role as an adapter molecule was reported.

Structure of $tRNA$ : The $tRNA$ has a secondary structure like clover leaf.

But its three dimensional structure depicts it as an inverted $L$-shaped molecule, $tRNA$ has five arms or loops as follows :

$(i)$ Anticodon loop : It has bases complementary to the code.

$(ii)$ Amino acid acceptor end : At his end, amino acids bind.

$(iii)$ $T$-loop : It helps in binding to ribosome.

$(iv)$ $D$-loop : It helps in binding aminoacyl synthetase.

$(v)$ Variable loop : it is variable in both nucleotide composition and in length.

$tRNAs$ are specific for each amino acid.

For initiation, there is another specific $tRNA$ that is another specific $tRNA$ that is referre initiator $tRNA.$

There are no $tRNAs$ for stop codons.

In figure, the secondary structure of $tRNA$ has been depicted that looks like a clover leaf.