Which of the following is used in recombinant $DNA$ technique?

In transformation,microparticles are bombarded with the help of a gene gun,which are made of ............ .

$A$ : $DNA$ ligase plays an important role in recombinant $DNA$ technology.
$R$ : The linking of antibiotic resistance gene with plasmid vector became possible by enzyme $DNA$ ligase.

Which restriction site is present in the $tet^{R}$ gene in $pBR322$?

Who constructed the first $r-DNA$ molecule?

The first restriction endonuclease was isolated from which of the following?