Which of the following method$(s)$ is used to introduce foreign $DNA$ into host cells?

$DNA$ can be introduced into any cell by:

Explain how recombinant $DNA$ is introduced into a host cell or a living organism.

Palaeontologists unearthed a human skull during excavation. $A$ small fragment of the scalp tissue was still attached to it. Only a little $DNA$ could be extracted from it. If the genes of the ancient man need to be analysed,the best way of getting a sufficient amount of $DNA$ from this extract is:

When foreign $\text{DNA}$ is inserted into any vector,it results in inactivation of any marker gene. This is used for selection of $......\ :-$

During the processing of the prohormone $proinsulin$ into the mature $insulin$—