Polymerase chain reaction is most useful in

In this process,$DNA$ fragments are transferred from the gel to a synthetic membrane.

For selection of recombinants,insertional inactivation of antibiotic marker has been superceded by insertional inactivation of a marker gene coding for a chromogenic substrate. Give reasons.

Which of the following steps are involved in the process of recombinant biotechnology? Arrange in correct order.
$I.$ Extraction of the desired gene product
$II.$ Amplification of the gene of interest
$III.$ Isolation of a desired $DNA$ fragment
$IV.$ Ligation of the $DNA$ fragment into a vector
$V.$ Insertion of recombinant $DNA$ into the host
Correct order is:

Diagrammatically represent the experimental steps in cloning and expressing a human gene (e.g.,the gene for growth hormone) in a bacterium like $E. coli$.

Select the correct sequence for $PCR$ (Polymerase Chain Reaction).