What conclusions were drawn from the Hershey and Chase experiment about DNA as the genetic material?

Sourav PanNovember 9, 2024

Answered step-by-step

The Hershey and Chase experiment, conducted in 1952 by Alfred Hershey and Martha Chase, was pivotal in establishing that DNA is the genetic material. Here are the key conclusions drawn from their work:

Key Conclusions from the Hershey and Chase Experiment

1. DNA is the Genetic Material:
   • The primary conclusion of the Hershey and Chase experiment was that DNA, not protein, serves as the genetic material in bacteriophages (viruses that infect bacteria). This was demonstrated through their use of radioactive isotopes to label DNA and proteins separately.
2. Experimental Design:
   • Hershey and Chase used two different batches of bacteriophages:
     • One batch was labeled with radioactive phosphorus (³²P), which is found in DNA but not in proteins.
     • The other batch was labeled with radioactive sulfur (³⁵S), which is present in proteins but absent in DNA.
   • They allowed these labeled phages to infect Escherichia coli (E. coli) bacteria.
3. Observation of Radioactivity:
   • After allowing the phages to infect the bacteria, they used a blender to separate the phage coats from the bacterial cells. They then centrifuged the mixture to separate the heavier bacterial cells from the lighter phage coats.
   • They found that:
     • Bacteria infected with phages labeled with radioactive DNA (³²P) were radioactive, indicating that DNA had entered the bacterial cells.
     • Bacteria infected with phages labeled with radioactive protein (³⁵S) were not radioactive, indicating that proteins did not enter the bacterial cells.
4. Implications for Genetic Inheritance:
   • The results indicated that it was the DNA from the bacteriophages that carried the genetic instructions necessary for producing new phage particles within the bacterial host. Since only DNA entered the bacteria and directed their machinery to produce more phages, this strongly supported the idea that DNA is responsible for heredity.
5. Confirmation of Previous Findings:
   • The Hershey and Chase experiment built upon earlier work, including experiments by Frederick Griffith and Oswald Avery, which suggested that DNA might be the hereditary material. Their findings provided definitive evidence that helped settle ongoing debates among scientists regarding whether proteins or nucleic acids were responsible for genetic inheritance.