Question

How did Harshey and Chase establish that the DNA is transferred from virus to Bacteria?

Answer 1

Hint: Harshey and Chase demonstrated that the genetic material in the bacteriophage is the DNA and not proteins through their experiments. It was widely accepted among all scientists.

Complete Answer:
Harshey and Chase chose Bacteriophage as the experimental organism. Bacteriophage is the virus that infects bacteria. Bacteriophage consists of the DNA and the protein coat called the capsid. They chose bacteriophage because it contains only protein and DNA. So the separation of the two was quite easy.

Harshey and Chase experiment:
- The radioactive labelling of the phage DNA and protein was done using radioactive sulphur and phosphorus.
- These radioactive labelled phages were used to infect E.coli.
- Centrifugation and blending of E.coli was done to remove virus particles.
- The bacteria that were infected with radioactive DNA became radioactive and the ones with radioactive proteins lost radioactivity.

Result: This shows that when the Bacteriophage infects the E.coli, the DNA enters the bacteria and not the proteins.

Additional Information: Radioactive phosphorus-32 was used to label DNA as phosphorus is present in DNA and sulphur-35 was used to label protein as sulphur is present in proteins.

Note: This experiment proved that the DNA is the genetic material not the protein. The DNA of the phage enters the bacterium through a tiny hole and the protein coat remains outside. The DNA as a genetic material opened doors for further applications like DNA fingerprinting, DNA forensics etc.