Give scientific reasons: The products prepared by recombinant $DNA$ technology have to undergo downstream processing.

Which one of the following statements is wrong with respect to separation of $DNA$ fragments on gel electrophoresis?

Which of the following statements are correct with respect to $DNA$ separation,isolation and visualization?
$A$. The cutting of $DNA$ is done by molecular scissors.
$B$. The $DNA$ fragments separate according to their size in an agarose gel,upon electrophoresis.
$C$. The separated $DNA$ fragments can be seen without staining when exposed to $UV$ light.
$D$. The separated $DNA$ fragments,when stained with ethidium bromide,can be seen in visible light.
Choose the correct answer from the options given below:

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

After the biosynthetic phase, the product is separated & purified by the process called :-

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 $Ca^{2+}$.