There are special proteins that help to open up $DNA$ double helix in front of the replication fork. These proteins are:

Discuss the significance of the heavy isotope of nitrogen in the Meselson and Stahl experiment.

$DNA$ polymerase links nucleotides by forming which type of bond?

Give scientific reasons: The replication of $DNA$ is bidirectional.

Given below are two statements:
Statement $I:$
$DNA$ polymerases catalyse polymerisation only in one direction,that is $5^{\prime} \rightarrow 3^{\prime}$.
Statement $II:$
During replication of $DNA$,on one strand the replication is continuous while on the other strand it is discontinuous.
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 $DNA$?