$DNA$ gyrase,the enzyme that participates in the process of $DNA$ replication,is a type of

In the process of $DNA$ replication, the mechanism where two strands separate and each serves as a template for the synthesis of a new strand is known as .......

During $DNA$ replication,Okazaki fragments on the lagging template are always formed in $A$ direction $B$.

An $E. coli$ cell with light $DNA$ is incubated in a culture medium containing a heavy isotope of nitrogen $(^{15}N)$. After $60$ minutes, find out the percentage of light $DNA$. (in $\%$)

Which of the following processes is related to reverse transcription?

Define the following terms:
$1.$ Template strand
$2.$ Semi-conservative replication