What data would Meselson and Stahl have expected if DNA replication was dispersive rather than semiconservative? [closed]

Question

What data would Meselson and Stahl have expected if DNA replication was conservative rather than semiconservative?

Answer:

In the first generation, there would be two bands, one of light density and one of heavy density. In the second generation there would still be two bands, one of light density and one of heavy density.

Question 1:

In the second generation, are the heavy-density bands getting closer to the end of the test tube, and the light-density bands closer to the top of the tube, than the first generation? (due to the larger number of DNA molecules)

What data would Meselson and Stahl have expected if DNA replication was dispersive rather than semiconservative?

Answer:

In the first generation, there would be one band, one of intermediate density. In the second generation there would still be one band, one of intermediate density.

Question 2:

Are the bands closer to the top of the test tube in the second generation than the first generation? (Because DNA molecules would become lighter) If this model was approved, could we see this change in the test tube? (Between first and second generation)

Answer 1

A few baseline ideas should be understood. 1. The assumption is made that Meselson and Stahl's cell line at the start of the experiment contains DNA composed entirely of the $N_{15}$ isotope. 2. DNA with a greater proportion of $N_{15}$ isotope is denser than DNA with lesser proportion of $N_{15}$ isotope. 3. Higher density DNA sinks lower in the test tube than lighter density DNA. (Same density DNA sinks to the same level.)

Q1: Let's follow 100 parent (generation 0) cells. If DNA replication was conservative, after they first replication (generation 1), we would expect 200 DNA strands. 100 strands come from the "parent" cells and are entirely composed of $N_{15}$ isotope (the conserved template strand). The other 100 strands come from "daughter" cells and are entirely composed of $N_{14}$ isotope (the newly synthesized strand). After the second replication then, we would expect 400 DNA strands. 200 strands come from the "generation 1" cells and share their DNA composition: 100 strands of $N_{15}$ isotope and 100 strands of $N_{14}$ isotope. The other 200 strands come from "daughter" cells and are entirely composed of $N_{14}$ isotope. Thus, in both generations, there are only DNA strands of 100% $N_{15}$ isotope and 100% $N_{14}$ isotope. The only difference is that the second generation has proportionally more DNA STRANDS composed entirely $N_{14}$ isotope than the first. Because the proportion of $N_{15}$ isotope and $N_{14}$ isotope in an INDIVIDUAL strand determines the strand's density, and because the strands in both generations comprise of 100% $N_{14}$ isotope strands and 100% $N_{15}$ isotope strands, the bands visible in the two test tubes are at the same level. They do not move closer to the ends of tube.

Q2: Yes this is correct. The first generation's DNA would all be ~50% $N_{15}$ isotope/~50% $N_{14}$ isotope strands. The second generation's DNA would all be ~25% $N_{15}$ isotope/~75% $N_{14}$ isotope strands. Strands of proportionally less $N_{15}$ isotope are lighter and thus closer to the top of the test tube.