The enzyme that breaks $H_2$ bonds in $DNA$ is

The $DNA$ strand showing replication using Okazaki fragments also shows

Reverse transcriptase is a ...........

Bacteria were grown in a medium containing a heavy isotope of nitrogen $(^{15}N)$ for many generations,and all their $DNA$ contained only heavy nitrogen. $A$ bacterium of this type was transferred to a normal medium and allowed to duplicate. After two divisions,the distribution of heavy $DNA$ is likely to be:

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 $DNA$?

In which type of $DNA$ replication,out of the two newly formed molecules,one is purely new and the other is entirely old?