Identify the following bioreactors.
$P \quad\quad Q$

Which of the following diagrams is correct for primer annealing in $PCR$?

In gel electrophoresis,the separated bands of $DNA$ are cut out and extracted from the gel piece. This step is called

How many types of primers are required for the amplification of a gene in $PCR$?

$A$ 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?

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.