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

$DNA$ is synthesized from viral $RNA$ using the enzyme:

Self-replication occurs in

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 $\%$)

Taylor and his colleagues proved that $DNA$ in chromosomes also replicates semi-conservatively. Which organism did they use for this experiment?

Give scientific reasons: The replication of $DNA$ is determined by $DNA$ itself.