Which of the following did Meselson and Stahl use in the experiment to prove semiconservative $DNA$ replication?

Semi-conservative replication of $DNA$ was first demonstrated in

During $DNA$ replication,why is it that the entire molecule does not open in one go? Explain the replication fork. What are the two functions that the monomers $(dNTPs)$ play?

Identify the given model.

Which of the following statements is incorrect $:-$

Given below are two statements,one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A):$ $\text{DNA}$ replication occurs within a small opening of the $\text{DNA}$ helix,referred to as the replication fork.
Reason $(R):$ During transcription,the discontinuously synthesized fragments of $\text{DNA}$ are joined by the enzyme $\text{DNA}$ ligase.
In the light of the above statements,choose the most appropriate answer from the options given below: