Which of the following is used as a vector for cloning genes in higher organisms?

The characteristics of a molecular probe are
$I.$ very long molecule
$II.$ double-stranded
$III.$ $DNA$ or $RNA$
$IV.$ complementary to a part of the desired gene
The correct pair is

The given figure represents the cloning vector $pBR322$ of $E. coli$. Which of the following options correctly identifies its components?

Which organism is most commonly used as a host in $r-DNA$ technology?

Select the option that excludes characteristics applicable to plasmids:
$(a)$. Circular $DNA$
$(b)$. Linear $DNA$
$(c)$. Present in all bacteria
$(d)$. Contain essential genes
$(e)$. Extra chromosomal self-replicating

$A$ plasmid without a selectable marker was chosen as a vector for cloning a gene. How does this affect the experiment?