........ make cuts at specific positions within the $DNA$.

The term 'disarmed' in a disarmed vector represents:

Given below are two statements.
Statement $I$: Restriction enzyme $BamHI$ has its recognition site in $tet^R$ region of $pBR322$.
Statement $II$: $E. coli$ having $pBR322$ with a desired $DNA$ if inserted at $BamHI$ site can grow in medium containing tetracycline.
In the light of the above statements, choose the correct answer from the options given below.

Which enzyme is used to join the ends of two strands of nucleic acid?

Restriction enzymes should not have more than one site of action in the cloning site of a vector. Comment.

Which microorganism is useful for $PCR$?