Describe Hershey’s and Chase’s experiments showing evidence for DNA as the genetic material.
The Correct Answer and Explanation is:
Correct Answer:
Hershey and Chase’s experiments used viruses that infect bacteria, called bacteriophages, to show that DNA is the genetic material, not protein.
Explanation
In 1952, Alfred Hershey and Martha Chase conducted a series of experiments to determine whether DNA or protein was the hereditary material that viruses use to reproduce inside cells. They used a type of virus called a bacteriophage, which infects bacteria. The bacteriophage consists of only two types of molecules: DNA and protein. This made it an ideal subject for testing which of these two components carried genetic instructions.
To identify the material injected into the bacteria, they used radioactive labeling. In one experiment, they labeled the protein coat of the virus with radioactive sulfur-35 (^35S), because sulfur is found in proteins but not in DNA. In another experiment, they labeled the DNA with radioactive phosphorus-32 (^32P), because phosphorus is found in DNA but not in proteins.
Next, the labeled viruses were allowed to infect bacterial cells. After the viruses injected their genetic material, Hershey and Chase used a blender to separate the empty virus coats from the infected bacterial cells. They then measured where the radioactivity was found.
In the first experiment, with ^35S-labeled proteins, they found the radioactivity remained outside the bacteria. In the second experiment, with ^32P-labeled DNA, the radioactivity was found inside the bacteria. Furthermore, the bacteria that received the radioactive DNA produced new viruses, showing that DNA carried the genetic information needed for replication.
These results clearly demonstrated that DNA, not protein, is the molecule responsible for carrying genetic information. The Hershey and Chase experiments were crucial in confirming that DNA is the genetic material in all living organisms, supporting earlier work by scientists like Avery, MacLeod, and McCarty. Their work laid the foundation for further discoveries about the structure and function of DNA, including the double helix model proposed by Watson and Crick.
