Question

This question is about the Mode of DNA replication: Meselson-Stahl experiment

4. The investigators "anticipated that a label which imparts to the DNA molecule an increased density" (Introduction, paragraph 1) might help reveal how atoms in parental DNA are distributed to progeny DNA molecules. What label did the investigators use to be able to detect differences among molecules?

Answer 1

Meselson-Stahl experiment was performed inorder to find out the mode of DNA replication; whether it could be Conservative, Semiconservative or Dispersive replication. So, inorder to prove this replication model, the investigators used radioactive Nitogen atom ie, N¹⁵. So that it gets incorporated into the Four different Nitrogen bases and as it is a heavy isotope of Nitrogen the density significantly differs from that of the Normal light isotope of Nitrogen ie; N¹⁴.