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

$A$ number of bacteria with recombinant $DNA$ of the same type form:

Plasmid $pBR322$ has a $PstI$ restriction enzyme site within the gene $amp^R$ that confers ampicillin resistance. If this enzyme is used for inserting a gene for $\beta$-galactosidase production and the recombinant plasmid is inserted into an $E. coli$ strain:

In gel electrophoresis,at which end is the sample loaded?

Which of the following is required for the amplification of a gene of interest by $PCR$?

Which chemical is utilised during the isolation of $DNA$ at the end of precipitation?