What is the function of a selectable marker?

Autonomously replicating circular extrachromosomal $\text{DNA}$ is called:

$PCR$ technique was invented by

The gene whose expression helps to identify the transformed cell is known as........

$Taq$ polymerase is isolated from a bacterium,$Thermus$ $aquaticus$.

$I.$ $Ori$ also controls the copy number of the linked $DNA$.
$II.$ If a foreign $DNA$ ligates at the $BamHI$ site of the tetracycline resistance gene in the vector $pBR322$,the recombinant plasmid loses the tetracycline resistance due to the insertion of foreign $DNA$.
Choose the correct option regarding the above statements.