3. Meselson-Stahl & Scientific Reasoning Explain how the Meselson-Stahl experiment was able to eliminate both the conservative and dispersive models of DNA replication. In your answer, discuss the predictions each model would have made after one and two rounds of replication, how these differ from the observed results, and why semi-conservative replication remains the only viable model.
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At the time, three models were proposed: conservative, semi-conservative, and dispersive. The experiment used isotopes of nitrogen ($$N^{15}$$ and $$N^{14}$$) to label DNA and track its distribution through replication. Show more…
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Conclusions from the Meselson-Stahl Experiment The Meselson-Stahl experiment (see Fig. $25-2$ ) proved that DNA undergoes semiconservative replication in $E$. coli. In the "dispersive" model of DNA replication, the parent DNA strands are cleaved into pieces of random size, then joined with pieces of newly replicated DNA to yield daughter duplexes. Explain how the results of Meselson and Stahl's experiment ruled out such a model.
Penny R.
Recall the famous Meselson-Stahl DNA replication experiment, which began with bacteria grown for many generations in a medium containing nitrogen-15 (15N) and then switched to a medium containing nitrogen-14 (14N). The resulting DNA products were subjected to centrifugation as shown in the figure below (where the lighter gray band represents a smaller amount of DNA than the darker gray bands). Which of the following models of DNA replication (conservative, semiconservative, or dispersive) would these results have supported? Give the name of the model AND describe it.
Adi S.
In 1958, Meselson and Stahl conducted an experiment to determine which of the three proposed methods of DNA replication was correct. Identify the three proposed models for DNA replication: 1. Conservative 2. Semiconservative 3. Dispersive Answer Bank: The Meselson and Stahl experiment starts with E. coli containing 15N/15N labeled DNA grown in 14N media. Which result did Meselson and Stahl observe by sedimentation equilibrium centrifugation to provide strong evidence for the semiconservative model of DNA replication? The first generation has hybrid 15N/14N DNA and the second generation has both hybrid 15N/14N DNA and 14N/14N DNA. No 15N/15N DNA was observed. Both the first and second generation have both 15N/15N DNA and 14N/14N DNA. No hybrid 15N/14N DNA was observed. The first generation has hybrid 15N/14N DNA and the second generation has hybrid 15N/14N DNA. No 15N/15N DNA nor 14N/14N DNA was observed.
Sri K.
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