Question

Describe how the Hershey-Chase experiment demonstrated that DNA is the genetic material, not protein as previously thought. Explain how they used radioactive isotopes and bacteriophages in their experiment and summarize their conclusions.

Answer 1

Harshey and chase experiment involved infecting bacterial cells with radioactively labelled bacteriophages in order to test whether radioactive protien is the one which is transffered or the DNA.(to be considered as genetic material).The bacterial cells were infeced with bacteriophages,blended to remove bacteriophages from cell and then centrifuged to get cells and supernatant separated.

Viruses were known to be composed of a protien shell and DNA.So,Harshey and Chase chose to uniquely label each wih a different isotope.Phosphorus is contained in DNA but no amino acids.So,radioactive phosphorus-32 was used to label DNA in T2 phage.Radioactive sulphur-35 was used to label protein sections of T2 phage because Sulphur is contained in protein not DNA.

They inserted radioactive elements in bacteriophages by adding isotope to seperate media within which bacteria were allowed to grow for 4 hours before bacteriophage introduction.Further process and conclusion is described in the following diagram:-By this experiment it was concluded that DNA is the genetic material which is passed on from an organism and not the protein.