Scientific Thinking 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. Understand the structure of bacteriophage T2: Bacteriophage T2 is a virus that infects bacteria, specifically E. coli. It consists of a protein coat surrounding DNA. This structure is crucial for understanding how Hershey and Chase designed their experiment.
2. Recognize the components to be labeled: Hershey and Chase used radioactive isotopes to label the different components of the bacteriophage. They used sulfur-35 (35S) to label the protein coat, as sulfur is found in proteins but not in DNA. They used phosphorus-32 (32P) to label the DNA, as phosphorus is a component of DNA but not of proteins.
3. Design the experiment: Hershey and Chase allowed the bacteriophages to infect the E. coli cells. During the infection process, the phage injects its genetic material into the host cell but the protein coat remains outside.
4. Analyze the results: After the bacteriophages had infected the E. coli cells, Hershey and Chase used a blender to separate the phage protein coats from the bacterial cells. They then used a centrifuge to separate the heavier bacteria-containing radioactive DNA from the lighter protein coats.
5. Interpret the findings: By examining which part of the phage (DNA or protein) entered the E. coli cells and carried the radioactivity, Hershey and Chase were able to determine that DNA, not protein, is the genetic material responsible for heredity.

Key Concepts

Bacteriophage Structure

Bacteriophages, or phages, are viruses that specifically infect bacteria. The structure of bacteriophages typically includes a protein coat (capsid) and genetic material, which can be either DNA or RNA. The T2 bacteriophage, used by Hershey and Chase, has a simple structure that allows it to inject its genetic material into a bacterial host, making it an ideal model for studying the role of DNA in heredity.

DNA as Genetic Material

The concept that DNA serves as the genetic material was a pivotal discovery in molecular biology. Prior to Hershey and Chase's experiments, proteins were thought to be the carriers of genetic information. Their work demonstrated that DNA, not protein, is responsible for heredity, as they showed that only the DNA from the bacteriophage entered the bacterial cells and directed the production of new phages.

Experimental Design in Scientific Research

Experimental design is crucial in scientific research as it outlines how to test hypotheses effectively. Hershey and Chase utilized a clever experimental setup involving radioactive labeling of DNA and protein to trace which component entered the bacterial cells. This design allowed them to conclusively determine that DNA was the genetic material, showcasing the importance of methodical planning in experiments.