In the $PCR$ technique,how are the two strands of $DNA$ separated?

In gel electrophoresis,the separated bands of $DNA$ are cut out and extracted from the gel piece. This step is called

The full form of $PCR$ is ...........

$A$ recombinant $DNA$ molecule was created by ligating a gene to a plasmid vector. By mistake,an exonuclease was added to the tube containing the recombinant $DNA$. How does this affect the next step in the experiment,i.e.,bacterial transformation?

Which of the following range of temperature is required for denaturation,annealing of primer,and primer extension of $PCR$ respectively?

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 $Ca^{2+}$.