In which of the following wells was undigested $DNA$ loaded?

Which of these is $NOT$ a method to make host cells 'competent' to take up $DNA$?

Recombinant $\text{DNA}$ is directly injected into the nucleus of an animal cell by $-$

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: In recombinant $DNA$ technology, lysozyme is used for disrupting bacterial cells while cellulase is for plant cells.
Reason $R$: Isolation of genetic material needs disruption of cells.
In the light of the above statements, choose the most appropriate answer from the options given below:

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.

$PCR$ is used for: