Select the correct option for a eukaryotic cell regarding the origin of replication and the number of replication forks.

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 $DNA$?

If a hybrid $DNA$ $(^{14}N-^{15}N)$ is allowed to undergo replication twice in a medium containing nucleotides with $^{15}N$ base,then what proportion of light,heavy,and hybrid $DNA$ will be obtained respectively?

In a nucleus,the number of ribonucleoside triphosphates is $10$ times the number of deoxyribonucleoside triphosphates,but only deoxyribonucleotides are added during $DNA$ replication. Suggest a mechanism.

Who used heavy nitrogen $N^{15}$ for proving the semiconservative way of $DNA$ replication?

Name a few enzymes involved in $DNA$ replication other than $DNA$ polymerase and ligase. Name the key functions for each of them.