Which of the following is not a method of introducing alien $DNA$ into host cells?

Which one of the following equipments is essentially required for growing microbes on a large scale for the industrial production of enzymes?

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:

$A$ mixture of fragmented $DNA$ was electrophoresed in an agarose gel. After staining the gel with ethidium bromide,no $DNA$ bands were observed. What could be the reason?

Identify the given figure.

$DNA$ fragments can be separated by using which of the following techniques?