In 1952, Hershey and Chase conducted a series of experiments indicating that DNA was the physical carrier of heredity.

Biology · Middle School · Sun Jan 24 2021

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Explanation : The most well-known Hershey-Chase experiment was the final experiment, also called the Waring Blender experiment, through which Hershey and Chase showed that phages only injected their DNA into host bacteria, and that the DNA served as the replicating genetic element of phages. 

In the previous experiment, Hershey and Chase found evidence that phages injected their DNA into host bacteria. In the Waring Blender experiment, the scientists found that the phages did not inject any part of their protein coats in the host bacteria and the protein coats remained outside the bacteria, adhered to the bacterial membranes. For their experiment, Hershey and Chase prepared two samples of infected E. Coli. They infected one sample with radioactive phosphorus-labeled phages, and the other sample with radioactive sulfur-labeled phages. Then, they stirred each sample in a Waring Blender, which was a conventional kitchen blender. They used a blender because centrifuges spun too fast and would destroy the bacterial cells. The shearing forces of the blender removed the phage particles that adhered to the bacterial membranes, but preserved the integrity of the cells and most of the phage material that entered the cell. In the phosphorus-labeled sample that marked DNA but not protein, the blender removed forty percent of the labeled particles. In the sulfur-labeled sample that marked protein but not DNA, the blender removed eighty percent of the labeled particles. Those results indicated that the blender removed much more of the protein parts of the phage than the DNA parts, suggesting that the protein likely remained adhered to the outside of the cell during infection. Since the protein remained outside the cell, it could not be the replicating genetic material.

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