Which of the following statements is correct in the context of observing $DNA$ separated by agarose gel electrophoresis?

Polymerase chain reaction is most useful in

An artificial process of infecting cells with naked viral $DNA$ is:

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:

What is the effect of high temperature $(94^{\circ}C)$ on $DNA$?

Identify the following bioreactors.
$P \quad\quad Q$