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

Main steps in the formation of Recombinant $DNA$ are given below. Arrange these steps in a correct sequence.
$A$. Insertion of recombinant $DNA$ into the host cell
$B$. Cutting of $DNA$ at specific location by restriction enzyme
$C$. Isolation of desired $DNA$ fragment
$D$. Amplification of gene of interest using $PCR$
Choose the correct answer from the options given below:

What is the first step in the Southern Blot technique?

The figure below shows three steps $(A, B, C)$ of a process. Select the option giving the correct identification $:-$

It increases the efficiency with which $DNA$ enters the bacterium through pores in its cell wall.

Describe briefly the following:
$(a)$ Origin of replication
$(b)$ Bioreactors
$(c)$ Downstream processing