The success of an experiment often depends on choosing an appropriate organism to study. For example, Gregor Mendel was able to deduce the fundamental principles in genetics in part because of his choice of the pea plant. Reviewing Module 10.1, how did Hershey and Chase take advantage of the unique structural properties of bacteriophage T2 to determine the genetic material?

Verified step by step guidance

1. Review the structure of bacteriophage T2: Bacteriophage T2 is a virus that infects bacteria. It consists of a protein coat (capsid) and DNA inside the capsid. This structural simplicity makes it an ideal organism for studying the genetic material, as it has only two main components to analyze: protein and DNA.
2. Understand the experimental design: Hershey and Chase used radioactive isotopes to label the two components of the bacteriophage. They labeled the DNA with radioactive phosphorus-32 (32P), since DNA contains phosphorus but no sulfur. They labeled the protein coat with radioactive sulfur-35 (35S), since proteins contain sulfur but no phosphorus.
3. Describe the infection process: The bacteriophage attaches to a bacterial cell and injects its genetic material into the host. The protein coat remains outside the bacterial cell, while the genetic material enters the cell to direct the production of new viruses.
4. Explain the separation of components: After allowing the bacteriophages to infect the bacteria, Hershey and Chase used a blender to separate the phage protein coats from the bacterial cells. They then used a centrifuge to isolate the bacterial cells from the rest of the mixture.
5. Analyze the results: They measured the radioactivity in the bacterial cells and the surrounding solution. They found that the radioactive phosphorus (32P) was inside the bacterial cells, indicating that DNA was the genetic material injected by the phage. The radioactive sulfur (35S) remained in the solution, showing that the protein coat did not enter the bacterial cells.

Key Concepts

Bacteriophage Structure

Bacteriophages, or phages, are viruses that specifically infect bacteria. The T2 bacteriophage consists of a protein coat (capsid) and a DNA core. This simple structure allows researchers to study the role of DNA in heredity, as the phage injects its genetic material into the host bacterium, leading to the production of new phages.

Hershey-Chase Experiment

The Hershey-Chase experiment, conducted in 1952, utilized T2 bacteriophages to determine whether DNA or protein was the genetic material. By labeling the DNA with radioactive phosphorus and the protein with sulfur, they tracked which component entered the bacterial cells. The results showed that only the DNA entered the cells, confirming that DNA is the genetic material.

Genetic Material

Genetic material refers to the molecules that carry the genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses. In most organisms, this material is DNA, which encodes the information necessary for building proteins and regulating cellular activities. The identification of DNA as the genetic material was a pivotal moment in molecular biology.