Question

How did Hershey and Chase established that DNA is transferred from virus to bacteria

Answer 1

Hershey and Chase conducted a series of experiments that helped to confirm that DNA is the genetic material. They worked on bacteriophages which are the viruses that infect bacteria.

• When a bacteriophage infects a bacterium, the viral genetic material gets attached with the bacterial genetic material and then, bacteria treats the viral genetic material as its own to synthesize more viral particles.
  
• Hershey and Chase worked to discover whether it was a protein or DNA that entered the bacteria from the virus.
  
• They labelled some phages with radioactive sulphur and the others with radioactive phosphorus.
  
• These radioactive phages were used to infect E. coli.
  
• Then, E.coli was blended and centrifuged to remove viral particles.
  
• It was observed that bacteria with radioactive DNA were radioactive while those with radioactive proteins lost their radioactivity.
  
• This showed that it is the DNA that enters the bacteria from viruses and not proteins. Hence, it was concluded that DNA is the genetic material.