When $DNA$ fragments are stained with ethidium bromide and viewed under $UV$ light,what color do they appear?

During the process of gene amplification using $PCR$,if very high temperature is not maintained in the beginning,then which of the following steps of $PCR$ will be affected first?

While doing a $PCR$,the 'denaturation' step is missed. What will be its effect on the process?

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.

Plant cells are bombarded with high-velocity micro-particles of ........... coated with $DNA$ in a method known as gene gun.

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