Biochemical nature of Transforming Principle
Bacteriologists performed a series of experiments to identify the Transforming Principle.
- Transforming principle precipitated with alcohol. This showed it was not Carbohydrate.
- Transforming principle could not be destroyed with Proteases. Thus, it was not Protein.
- Transforming principle could not be destroyed with Lipases. This proved it was neither Lipids.
- Transforming principle could not be inactivated with Ribonuclease, hence not RNA.
- Transforming principle could be inactivated with Deoxyribonuclease
Transforming principle was DNA. Therefore, DNA was the genetic material.
Hershey-Chase Experiment
Hershey-Chase experiment was performed in 1952 to further confirm that DNA was the genetic material. They experimented with Bacteriophages. Bacteriophages are the viruses that infect & replicate within bacteria.
Bacteriophages were grown in two different mediums.
- Some bacteriophages were grown in radioactive phosphorus medium. It was found that these Bacteriophages came up with radioactive DNA
- Some bacteriophages were grown in radioactive sulfur medium. It was found that these Bacteriophages with radioactive protein.
- Bacteriophages with Radioactive DNA were brought in contact with bacteria
- Bacteria got infected
- Agitated in a blender to separate phage particles from bacterial cells
- Centrifugation leaves Phage particles as supernatant
- Bacterial cells were found to be radioactive
- No radioactivity was detected in the phage particles
It was therefore concluded that it was not the proteins, rather DNA which entered into the bacteria. Therefore, DNA causes the replication of viruses inside the bacteria.
DNA was thus proved to be the genetic material.
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