The mode of $DNA$ replication is predominantly ......

$^{15}N$ labeled $E. coli$ is allowed to grow in a $^{14}N$ medium. The two strands of the $DNA$ molecule of the first generation bacteria have:

For the strand separation and stabilisation during $DNA$ replication,which of the following set of enzymes and proteins are required?

Given below are the two statements.
Statement $I$: In prokaryotes,there is only one replicon,however,in eukaryotes,there are several replicons in tandem.
Statement $II$: The two separated strands in a replicon of $DNA$ are prevented from rejoining by helicase enzyme.
In the light of the above statements,choose the correct answer from the options given below.

Which one of the following correctly represents the manner of replication of $DNA$?

For how long should bacteria be cultured in a $^{14}N$ medium after being transferred from a $^{15}N$ medium so that the extracted $DNA$ consists of equal amounts of hybrid $DNA$ and light $DNA$?