Pathogenic bacteria gain resistance to antibiotics due to changes in their:

The function of the 'ori' site in a vector is to

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: When a particular restriction enzyme cuts a strand of $DNA$,overhanging stretches or sticky ends are formed.
Reason $(R)$: Some restriction enzymes cut the strand of $DNA$ a little away from the centre of the palindromic site.
In the light of the above statements,choose the correct answer from the options given below:

About gene gun method:
$I.$ This method is also known as biolistic technique.
$II.$ In this method,cells are bombarded with high-velocity micro-particles of gold or tungsten coated with $DNA$ in plants.
$III.$ Important crop plants like maize,rice,and wheat have now been transformed by this method.
Which of the statements given above are correct?

How many recognition sites are present for each restriction enzyme in the cloning vector $pBR322$?

$A$ gene library or $DNA$ library contains a collection of: