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

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?

The process of $DNA$ multiplication is called:

$^{15}N$ 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:

$A$ $N^{15}-N^{15}$ $\text{DNA}$ molecule is continuously replicated in $N^{14}$ medium,then what is the percentage of heavy $\text{DNA}$ in the $4^{\text{th}}$ generation (in $\%$)?

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.