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

When $DNA$ fragments stained with ethidium bromide are viewed under $UV$ radiation,how do they appear?

Select the correct statement.

Which of the following should be chosen for best yield if one has to produce a recombinant protein or enzyme on a large scale,using microbial,plant,animal,or human cells?

Refer to the following statements for agarose-gel electrophoresis:
$(a)$ The $\text{DNA}$ fragments resolve according to their size.
$(b)$ The separated $\text{DNA}$ fragment can be visualised only after staining with ethidium bromide followed by exposure to $UV$ radiation.
$(c)$ $\text{DNA}$ is always loaded into the well.
$(d)$ The smallest fragment of $\text{DNA}$ is near the well.
Choose the correct statements:

During the purification process for recombinant $DNA$ technology,the addition of chilled ethanol precipitates out: