After $4$ $PCR$ cycles,how many $DNA$ molecules are formed from one $DNA$ template molecule?

Study the following diagram of the Polymerase Chain Reaction $(PCR)$ and identify $A, B$ and $C$.

$DNA$ precipitation out of a mixture of biomolecules can be achieved by treatment with

Assertion : Insertion of recombinant $DNA$ within the coding sequence of $\beta -$ galactosidase results in colourless colonies.
Reason : Presence of insert results in inactivation of enzyme $\beta -$ galactosidase known as insertional inactivation.

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

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