In cloning vectors,antibiotic resistant genes are helpful for

$A$ : $Pst I$ generates single-stranded overhanging stretches in $DNA$ after digestion that facilitate ligation.
$R$ : These short extensions can form hydrogen bonds with their complementary counterparts,which are then sealed by $DNA$ ligase to form phosphodiester bonds.

$A$ single-stranded piece of nucleic acid tagged with a radioactive molecule,which is used to detect a specific gene through hybridization,is called:

Which of the following can be considered as molecular scissors?

Which enzyme joins the broken strands of $DNA$?

Plasmids are suitable vectors for gene cloning because