Agarose gel electrophoresis is used to separate $DNA$ fragments. The $DNA$ fragments separate due to . . . . . . .

Consider the following statements about $PCR$:
$I.$ Polymerase Chain Reaction $(PCR)$ is a technique of synthesizing multiple copies of the desired gene in vitro.
$II.$ This technique was developed by Kary Mullis in $1985$.
$III.$ $A$ single $PCR$ amplification cycle involves three basic steps: denaturation,annealing,and extension.
Which of the statements given above are correct?

$I.$ $DNA$ being a hydrophilic molecule cannot pass through cell membranes.
$II.$ The bacteria should be made competent to accept the $DNA$ molecule.
The correct option regarding the above statements is:

During the process of isolation of $DNA$,chilled ethanol is added to

The transfer of protein from electrophoretic gel to nitrocellulose membrane is known as

The primer extension during $PCR$ cycle requires the temperature range of . . . . . . .