Hershey and Chase Experiment

Summary

In 1952, Alfred Hershey and Martha Chase conducted an experiment using bacteriophages to demonstrate that DNA, not protein, is the genetic material. By growing viruses in media with radioactive phosphorus and sulfur, they tracked which component was transferred to bacteria during infection. The results showed that DNA, labeled with phosphorus, entered the bacteria, while proteins, labeled with sulfur, did not. This pivotal experiment provided strong evidence that DNA carries genetic information, transforming our understanding of molecular genetics.

Takeaways

• 😀 A bacteriophage is a virus that infects bacteria.
• 😀 Alfred Hershey and Martha Chase conducted an experiment in 1952 to demonstrate that DNA is the genetic material.
• 😀 The experiment involved growing viruses in mediums with radioactive phosphorus and sulfur.
• 😀 Viruses grown in radioactive phosphorus medium contained radioactive DNA.
• 😀 Viruses grown in radioactive sulfur medium contained radioactive proteins.
• 😀 After infection, the viral coats were removed from the bacteria by agitation.
• 😀 Viral particles were separated from the bacteria using a centrifuge.
• 😀 The bacteria were tested for traces of radioactivity after infection.
• 😀 Bacteria infected with viruses containing radioactive phosphorus had radioactive DNA, indicating DNA was transferred from virus to bacteria.
• 😀 Bacteria infected with viruses containing radioactive sulfur had no radioactive sulfur, indicating proteins were not transferred from virus to bacteria.
• 😀 This experiment led to the conclusion that DNA is the genetic material passed from virus to bacteria.

Q & A

What is a bacteriophage?

A bacteriophage is a virus that infects bacteria.

Who were the scientists responsible for demonstrating that DNA is the genetic material?

Alfred Hershey and Martha Chase were the scientists who demonstrated that DNA is the genetic material in 1952.

What experimental approach did Hershey and Chase use to demonstrate that DNA is the genetic material?

Hershey and Chase used bacteriophages grown in media containing radioactive phosphorus and sulfur to track DNA and protein transfer to bacteria.

Why did Hershey and Chase use radioactive phosphorus and sulfur in their experiment?

Radioactive phosphorus was used to label DNA and radioactive sulfur was used to label proteins, allowing Hershey and Chase to track which component was passed from the virus to the bacteria.

What did the bacteriophages grown in radioactive phosphorus contain?

The bacteriophages grown in radioactive phosphorus contained radioactive DNA.

What did the bacteriophages grown in radioactive sulfur contain?

The bacteriophages grown in radioactive sulfur contained radioactive proteins.

What happened after the viruses were allowed to infect the bacteria?

After infection, the viral coats were removed from the bacteria through agitation, and the viral particles were separated from the bacteria using a centrifuge.

How did Hershey and Chase identify which substance was passed from the virus to the bacteria?

After separating the virus and bacteria, they tested the bacteria for traces of radioactivity. The presence of radioactive DNA indicated that DNA was passed to the bacteria.

What was the key finding from the experiment regarding the protein?

The bacteria infected with the virus containing radioactive sulfur showed no radioactivity in their sulfur, indicating that the proteins were not passed from the virus to the bacteria.

What conclusion did Hershey and Chase draw from their experiment?

Hershey and Chase concluded that DNA, not protein, was the genetic material passed from the virus to the bacteria.