$pBR-322$ is frequently used as a cloning vector. What is it?

Using recombinant technology,genes from a donor cell can be transplanted into a bacterium for $DNA$ replication and protein synthesis. The kinds of cells that can be used as a donor in this technology are

Identify the desirable characteristics for a plasmid used in $rDNA$ technology from the following.
$A$. Ability to multiply and express outside the host in a bioreactor.
$B$. $A$ highly active promoter
$C$. $A$ site at which replication can be initiated
$D$. One or more identifiable marker genes
$E$. One or more unique restriction sites.

Which structure is involved in genetic engineering?

Give scientific reasons: In recombinant $DNA$ technology,the use of endonuclease is more proper than exonuclease.

Genetic engineering is possible because