Which of the following represents an advantage of growing cells in continuous culture as compared to a shake flask?

The different basic steps of genetic engineering are given below randomly:
$I.$ Identification of $DNA$ with desirable genes
$II.$ Gene transfer
$III.$ Maintenance of $DNA$ in host and gene cloning
$IV.$ Introduction of $DNA$ into host to form recombinant $DNA$
Which of the following represents the correct sequence of steps?

Choose the correct statement:
$P -$ Endonucleases cut the $DNA$ at a specific site inside the $DNA$.
$Q -$ $A$ stirred-tank reactor is usually square in shape.
$R -$ In order to force bacteria to take up the plasmid,the bacterial cells must first be made 'competent' to take up $DNA$ by treating them with a divalent cation like $Ca^{2+}$.

In a chemical process,the $DNA$ fragments produced by restriction endonucleases can be separated by:

In a mixture,$DNA$ fragments are separated by

Which of the following techniques is $NOT$ used for introducing $DNA$ into a host cell in $r-DNA$ technology?