What is the significance of adding proteases at the time of isolation of genetic material $(DNA)$?

$I.$ $DNA$ being a hydrophilic molecule cannot pass through cell membranes.
$II.$ The bacteria should be made competent to accept the $DNA$ molecule.
The correct option regarding the above statements is:

When foreign $\text{DNA}$ is inserted into any vector,it results in inactivation of any marker gene. This is used for the selection of $........$ ?

Which statements are correct for gel electrophoresis to separate $\text{DNA}$ fragments?
$(a)$ $\text{DNA}$ is a negatively charged molecule and so it is loaded on the gel towards the anode terminal.
$(b)$ $\text{DNA}$ fragments travel along the surface of the gel whose concentration does not affect the movement of $\text{DNA}$.
$(c)$ Smaller the size of $\text{DNA}$ fragments,larger is the distance it travels through it.
$(d)$ Pure $\text{DNA}$ can be visualized directly by exposing it to $\text{UV}$ radiation.

How can a recombinant protein be obtained?

Give scientific reasons: Hepatitis $B$ and Bird flu $DNA$ vaccines are called Recombinant $DNA$ vaccines.