$A$ probe is used in which stage of genetic engineering?

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

The $Polyethylene \ Glycol$ $(PEG)$ method is useful for which of the following?

In a bioreactor,through which system can a small volume of culture be withdrawn periodically?

In the above represented plasmid,an alien piece of $\text{DNA}$ is inserted at the $\text{EcoRI}$ site. Which of the following strategies will be chosen to select the recombinant colonies?

Which of the following techniques is most commonly used to separate $DNA$ molecules by size?