Question

To determine the semi-conservative nature of DNA replication, Meselson and Stahl performed the following experiment: Cells were grown in 15N for several generations and then shifted to 14N medium. Samples of cells were taken before the shift to 14N (generation 0) and then after multiple rounds of replication in 14N. The DNA was isolated from cells and subjected to centrifugation in gradient. The following results were obtained after 2 rounds of replication. Which of the following would result from a third round of replication in this experiment?

0 - heavy band on 15N

1- heavy band on hybrid

2- 1/2 hybrid 1/2 14N bands

a. one heavy band and one intermediate band b. one light band and one intermediate band c. one heavy band, one light band and one intermediate band d. one heavy band

Answer 1

Answer --

​​​​​In this question option c (one heavy band one light band and one intermediate band ) will be correct  

mesalson and sthal experimented to proved replication is a semicongervative .

In this experiment After the first replication have found hybrid DNA in which one strand is radiolabbled and another strand is non radiolabbled. In the next round of replication the have found N14, N14 band . another next round of replication three bans are found but in this case light band is more dark. Mean increasing the number of replication as well as light band (N14 N14 ) is more dark .