It is used to detect $HIV$ in suspected $AIDS$ patient and detect mutations in genes in suspected cancer patient too.

Polymerase chain reaction is most useful in

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:

Which of the following is added to precipitate purified $DNA$?

Select the correct statements from the following:

With respect to $DNA$ fragmentation:
Statement $A$: Gel electrophoresis and elution are two important processes.
Statement $B$: After staining with ethidium bromide,it has to be exposed to $UV$ light.