Hersheychase Experiment

In 1952, two American researchers, Martha Chase and Alfred Hershey, set out to test whether DNA or protein was the hereditary material viruses transfer when viruses enter a bacterium. Viruses that infect bacteria are called bacteriophages, or just phages. As shown in Figure 10-3 in step Q, Hershey and Chase used radioactive isotopes to label the protein and DNA in the phage. They used radioactive sulfur (35S) to label protein and radioactive phosphorus (32P) to label DNA. Then, they allowed protein-labeled and DNA-labeled phage to separately infect Escherischia coli (abbreviated E. coli) bacteria. In step ©, they removed the phage coats from the cells in a blender. They then used a centrifuge in step © to separate the phage from the E. coli. They found that all of the viral DNA and little of the protein had entered E. coli cells. They concluded that DNA is the hereditary molecule in viruses.

figure 10-3

The experiment of Hershey and Chase showed that DNA carries hereditary information from bacteriophages into the bacteria they infect.

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