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  • Hershey and Chase carried out their experiment under three steps : (a) Infection, (b) Blending, and (c) Centrifugation. Explain each one of these steps that helped them to prove that DNA is the hereditary material.  

Hershey and Chase carried out their experiment under three steps :
(a) Infection, (b) Blending, and (c) Centrifugation. Explain each one of these steps that helped them to prove that DNA is the hereditary material.

 

 

 

 
 
 
 
 

Answers (1)


The unequivocal proof that DNA is the genetic material came from the experiments of Alfred Hershey and Martha Chase (1952). They worked with viruses that infect bacteria called bacteriophages. They grew some viruses on a medium that contained radioactive phosphorus and some others on the medium that contained radioactive sulfur. Viruses grown in the presence of radioactive phosphorus contained radioactive DNA but not radioactive protein because DNA contains phosphorus but protein does not. Similarly, viruses grown on radioactive sulfur contained radioactive protein but not radioactive DNA because DNA does not contain sulfur.

1. Radioactive phages were allowed to attach to E. coli bacteria.

2. Then, as the infection proceeded, the viral coats were removed from the bacteria by agitating them in a blender.

3. The virus particles were separated from the bacteria by spinning them in a centrifuge.

4. Bacteria that were infected with viruses that had radioactive DNA were radioactive, indicating that DNA was the material that passed from the virus to the bacteria.

5. Bacteria that were infected with viruses that had radioactive proteins were not radioactive. This indicates that proteins did not enter the bacteria from the viruses. DNA is, therefore, the genetic material that is passed from virus to bacteria.

Posted by

Priyanka Kumari

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