Meselson-Stahl experiment

The Meselson-Stahl experiment is described in M. Meselson and F. W. Stahl, ProcNatl AcadSci USA 44 671-682 (1958). 

The Meselson-Stahl experiment (see Fig. 25-2) proved that DNA undergoes semiconservative replication ini , 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. In the Meselson-Stahl experiment, each strand would contain random segments of heavy and light DNA. Explain how the results of Meselson and Stahl s experiment ruled out such a model. 

Explain how the Meselson-Stahl experiment supports the semiconservative model of DNA replication. 

In the Meselson-Stahl experiment, why was a nitrogen isotope chosen rather than a carbon isotope ... 

The Meselson-Stahl experiment resulted in a single band of DNA on CsCl gradient centrifugation after one round of cell division. Its density was intermediate between heavy and light DNA. This could only occur if the newly synthesized dsDNA contained an old light strand and a new heavy strand. 

In the Meselson-Stahl experiment all of the nitrogen was N15. To accomplish the same effect with a carbon isotope all of the carbon in the medium would have to be isotopically pure in both phases of the experiment. This would be prohibitively expensive. 

Figure 4.14 The Meselson-Stahl experiment proves DNA replicates semiconservatively. 

Reflect and Apply In the Meselson-Stahl experiment that established the semiconservative nature of DNA replication, the extraction method produced short fragments of DNA. What sort of results might have been obtained with longer pieces of DNA ... 

If the original Meselson-Stahl experiment had used longer pieces of DNA, the results would not have been as clear-cut. Unless the bacteria were synchronized as to their stage of development, the DNA could have represented several generations at once. 

Outline the Meselson-Stahl experiment and relate it to semiconservative replication. Define the melting temperature (T for DNA and relate it to the separation of the strands of duplex DNA. Describe annealing. 

Interview between Pauling and then prospective graduate student Matthew Meselson, who during his subsequent tenure with Pauling did the Meselson-Stahl experiment, which proved the semiconservative nature of DNA replication. 

We have just mentioned a cell-free system derived from viruses and microorganisms. However, evidence for the semiconservative nature of DNA reduplication has also been obtained in higher plants. One piece of evidence consisted in repeating an experiment which had previously been carried out by Meselson and Stahl on bacteria and which is named after them the Meselson-Stahl experiment. 

The Meselson-Stahl experiment brings evidence for the semiconservative nature of DNA reduplication at the molecular level. However, in Taylor s experiments a similar demonstration was possible at the level of the chromosomes by using the technique of autoradiography. 

Fig. 137. The Meselson-Stahl experiment. The tracings of the curves in the middle column represent the amounts of and hybrid DNA found in each...

FIGURE 18.1 The Meselson-Stahl experiment, (a) Isopycnic centrifugation of DNA. (b) Results of the experiment... 

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