Question Video: Recalling the Results of the Hershey and Chase Experiment | Nagwa Question Video: Recalling the Results of the Hershey and Chase Experiment | Nagwa

Question Video: Recalling the Results of the Hershey and Chase Experiment Biology • Third Year of Secondary School

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The diagram provided shows a simple outline of an experiment carried out by Hershey and Chase. They radioactively labeled different parts of a bacteriophage (a virus that infects bacterial cells) to determine what material was used to infect bacteria. What did the experiment determine?

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Video Transcript

The diagram provided shows a simple outline of an experiment carried out by Hershey and Chase. They radioactively labeled different parts of a bacteriophage, a virus that infects bacterial cells, to determine what material was used to infect bacteria. What did the experiment determine? (A) Proteins are the genetic material transferred to bacteria. (B) DNA is the genetic material transferred to bacteria. (C) DNA and proteins are transferred from bacteriophages to bacteria. Or (D) bacteriophages only infect bacterial cells that do not contain DNA.

This question asks us about a famous experiment carried out by Alfred Hershey and Martha Chase in 1952. In order to answer the question correctly, let’s review what these experiments entailed. Hershey and Chase utilized bacteriophages. As indicated by their name, these are viruses that infect bacterial cells. You might recall that viruses require a host cell, like a bacteria, to replicate and proliferate. Hershey and Chase knew that these viruses were made of two parts: the protein shell and the viral DNA inside. But Hershey and Chase did not know how bacteriophages infect the bacteria: was it by transferring their DNA or their proteins?

In order to determine this, Hershey and Chase radioactively labeled these two different components of the bacteriophage, the proteins and the DNA, with different radioactive markers called isotopes. Because DNA contains high amounts of phosphorus, Hershey and Chase used radioactively labeled phosphorus to visualize this component. On the other hand, they used radioactively labeled sulfur in order to visualize proteins such as the capsid. This is because proteins, but not DNA, contain the unique molecule sulfur in some of their amino acids.

With these differentially labeled bacteriophages, Hershey and Chase then infected bacterial cells. And afterward, they centrifuged the resulting solution in order to separate cells from viral particles. Only the radioactively labeled DNA was detected inside the bacterial cells. This is because bacteriophages transmit genetic information during infection. Their protein structures, such as capsids, do not enter the cell, so these were only visualized in the layer containing viral particles.

Now that we have reviewed the experiments of Hershey and Chase, we are able to correctly answer this question. The correct answer is (B). The experiment determined that DNA is the genetic material transferred to bacteria.

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