What is the ultimate objective of $r-DNA$ technology?

Which of the following is the correct sequence of steps in the Polymerase Chain Reaction $(PCR)$?

Stirred-tank bioreactors have been designed for

What are bioreactors?

$A$ probe is used in which stage of genetic engineering?

Study the given figure carefully and select the correct statements regarding this.
$I.$ It represents typical agarose gel electrophoresis showing differential migration of $DNA$ fragments.
$II.$ Lane $1$ contains undigested $DNA$ fragments.
$III.$ Lanes $2$ to $4$ contain digested $DNA$ fragments.
$IV.$ Smallest $DNA$ bands are present at $(A)$ position and largest $DNA$ bands are present at $(B)$ position.