DNA as Genetic Material - Hershey And Chase Experiment - Practice Questions & MCQ

Updated on Sep 18, 2023 18:34 AM

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The unequivocal proof of DNA as the genetic material came from the studies on a

bacterium

fungus

viroid

bacterial virus

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Hershey & Chase Experiment

The proof for DNA as a genetic material came from the experiment performed by Alfred Hershey and Martha Chase (1952).
They carried out some experiments with the viruses that infect bacteria. These viruses are called bacteriophages.
The bacteriophage attaches to the bacteria and its genetic material then enters the bacterial cell.
The bacterial cell treats the viral genetic material as if it was its own and subsequently manufactures more virus particles.
Hershey and Chase worked to discover whether it was protein or DNA from the viruses that entered the bacteria.
For this, they took two separate media for growing these bacteriophages.
Out of two, one medium contained radioactive phosphorus and the other medium contained radioactive sulphur.
Viruses (bacteriophage) were then grown on each medium.
The viruses grown in the presence of radioactive phosphorus (32P) contained radioactive DNA (but not radioactive protein). This is because DNA contains phosphorus not protein.
In the same way, the viruses grown in the medium containing radioactive sulphur (35S) now contained radioactive protein (not radioactive DNA). This is because DNA does not contain sulphur.
These radioactive viruses (bacteriophages) were then allowed to attach to bacteria (E. coli).
As the process of infection with virus continued, the bacteria were agitated in a blender and the viral coats of the bacteria were removed.
The virus particles were separated from the bacteria by spinning them in a centrifuge.
Bacteria which were infected with viruses that had radioactive DNA were radioactive, indicating that DNA was the material that passed from the virus to the bacteria.
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