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

Which method is used to amplify a desired gene in large numbers?

The blue and white selectable markers have been developed which differentiate recombinant colonies from non-recombinant colonies on the basis of their ability to produce colour in the presence of a chromogenic substrate.
Given below are two statements about this method :
Statement-$I$ : The blue coloured colonies have $\text{DNA}$ insert in the plasmid and they are identified as recombinant colonies.
Statement-$II$ : The colonies without blue colour have $\text{DNA}$ insert in the plasmid and are identified as recombinant colonies.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which method is used to introduce $r-DNA$ directly into the nucleus of an animal cell?

What is meant by gene cloning?

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 $Ca^{2+}$.