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In the Meselson-Stahl experiment, which of the three modes of replication could be ruled out after one round of replication? after two rounds?
To determine: The reason that in the Meselson– Stahl experiment among the three modes of replication, the mode of replication that could be ruled out after oneround of replication.
Introduction: Messelson and Stahl experiment explained that semiconservative mode of replication used by bacterial cells to produce new DNA molecules.
Explanation of Solution
Messelson grew the E. coli cells for many generations in a medium containing 15NH4Cl. These cells then transferred to 14NH4Cl. After one round of replication, the conservative mechanism of DNA replication was ruled out as the intermediate density of DNA band found in the solution. DNA undergoes the semiconservative mode of replication.
Thus, the conservative mode of replication can be ruled out after one round of replication in case of Meselshon Stahl experiment.
To determine: The reason that in Meselson– Stahl experiment among the three modes of replication the mode of replication that could be ruled out after the second round of replication.
Introduction: Messelson and Stahlstudied the modes of DNA replication in bacteria by using nitrogen and its isotope in the medium. Bands of DNA replication was studied after each round of replication.
Explanation of Solution
Messelson grew the bacterial DNA in N15 and N14 media. After one round of replication in14N media, the band of the intermediate density of DNA was found.
After the second round of replication in14N media, the dispersive model of DNA replication was ruled out. The density of the DNA after the second round of replication was between the intermediate (both dark and light band) and “light” densities of DNA.
Thus, the dispersive model of DNA replication was ruled out after the second round of replication.
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Chapter 11 Solutions
Concepts of Genetics (12th Edition)
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Concepts of BiologyBiologyISBN:9781938168116Author:Samantha Fowler, Rebecca Roush, James WisePublisher:OpenStax College