You decide to repeat the Meselson-Stahl experiment,except this time you plan to grow the E.coli cells on light ¹⁴N medium for many generations and then transfer them to heavy ¹⁵N medium and allow them to grow for 2 additional generations (2 rounds of DNA replication).If the conservative model of DNA replication was correct,what is the expected distribution of DNA in the density gradient after two rounds of replication?

Question

Quizplus · Accepted Answer

If the conservative model of DNA replication is correct, then after two rounds of replication, there should be one band of light density (corresponding to the original DNA) and one band of heavy density (corresponding to the newly replicated DNA). This is because in the conservative model, the original double-stranded DNA molecule serves as a template for the synthesis of a completely new molecule, such that each daughter molecule is composed of one original strand and one newly synthesized strand. Therefore, after two rounds of replication, there should be a mix of both heavy and light DNA molecules present in the cell, leading to a corresponding mix of heavy and light bands in the density gradient.

You Decide to Repeat the Meselson-Stahl Experiment,except This Time You