What is the function of $PCR$?

The presence of a chromogenic substrate gives ............ coloured colonies.

To which charge is a $DNA$ molecule translocated during gel electrophoresis?

Match List $I$ with List $II$:

List $I$	List $II$
a) Visualization of $DNA$ in gel electrophoresis	i) Chitinase
b) Precipitation of $DNA$	ii) Lysozyme
c) Breaking of cell wall of bacteria	iii) Chilled ethanol
d) Breaking of cell wall of fungus	iv) Ethidium bromide

Codes:

How many types of primers are required for the amplification of a gene in $PCR$?

The steps involved in the Southern blot test are as follows:
$I.$ $X-ray$ film
$II.$ Electrophoresis
$III.$ Digestion with restriction enzyme
$IV.$ Ethidium bromide
$V.$ Radioactive probe
Choose the option having the correct sequential order of these events.